







How to calculate percentage change 
20070803 

Galland pose la question : I am working on graphs and I need to find the percentage of increase from one figure to another. How do I do that? For instance staff hours for 2006 were 28011 and for 2007 were 31230. How do I find the percentage of increase? Stephen La Rocque lui répond. 





Percentage change in productivity 
20170315 

Sunni pose la question : I'm working on a graph and I need to find the percentage of increase from one figure to another. How do I do that? For instance our department started with a workload of 1773 in Jan and ended with 341 in Dec. In addition to that we received 2088 new items from Jan  Dec with an average of 5 workers. How do I find the percentage of increased productivity if any? Penny Nom lui répond. 





The average rate of change of cot(t) 
20170118 

Brianna pose la question : Hello!
It's been a while since I've taken a math course, and I'm stuck on a problem in my calculus course.
The question is this:
Find the average rate of change of the function over the given interval.
h(t)=cot(t) a) [5pi/4, 7pi/4] Penny Nom lui répond. 





Water leaking from a trough 
20161228 

Kathryn pose la question : A trough is 6 m long, and has uniform crosssection of an equilateral triangle with sides 1 m.
Water leaks from the bottom of the trough, at a constant rate of 0.1 m3/min.
Find the rate at which the water level is falling when the water is 0.2m deep. Penny Nom lui répond. 





Percentage change 
20150114 

Jim pose la question : When using a scale e.g. 010, what is the formula for calculating percentage change. For example when someone answers a questionnaire where a question has a 010 scale, and they score a 4 first time, and then they answer the same questionnaire a different day, and they score an 8, how do I calculate the percentage change. Penny Nom lui répond. 





Percentage change 
20140509 

hi pose la question : the hw club had 46 members in sept. in april, the
club had 24 members. what was the percent of change in the hw club's membership from sept. to apan increase or decrease in membership?
ril? what is Penny Nom lui répond. 





$9.50 in coins 
20140115 

dana pose la question : you have $9.50 in coins. it has twice as many nickels as quarters and three times as many dimes as nickels. how many of each coin do you have? Penny Nom lui répond. 





When would one flip the inequality sign? 
20140109 

Natasha pose la question : Would one flip the inequality symbol in this equation: (explain why)
(9a)/(9) > 81
And please explain in what circumstances one would flip the inequality sign
THANKS! Penny Nom lui répond. 





Percent change in sales 
20130604 

Sui pose la question : Hi,
I would like to ask your favor for reviewing the following percent change in sales calculation, did I do it right? I am surprise/wondering with the big amount of the percentage result. Your assistance and guidance would be highly appreciate.
Sales for month of August 2000: 5,198,750 IDR
Sales for month of October 2000: 62,291,700 IDR
Difference = 62,291,700 IDR  5,198,750 IDR = 57,092,950 IDR
Percentage change = 57,092,950 IDR : 5,198,750 IDR = 10.98 X 100 = 1,098%
Sales for month of February 2008: 1,664,800 IDR
Sales for month of August 2008: 161,715,307 IDR
Difference = 161,715,307 IDR  1,664,800 IDR = 160,050,507 IDR
Percentage change = 160,050,507 : 1,664,800 = 96.14 X 100 = 9,614%
Thanking you,
Sui Penny Nom lui répond. 





Inverting fractions and percentage 
20130518 

Carlos pose la question : If I calculate the percentage change between two fractions, say,
1/100 and 2/100, I get 100% change. Now, if I flip denominator
and numerator, 100/1 and 100/2, and repeat the calculation, I
get a 50% change. Why are the percentages different?
Thank you very much Penny Nom lui répond. 





Increasing and decreasing sales 
20130306 

Meghan pose la question : Pace Design's sales increased by 30% in the first year, increased by 60% in the second year, decreased by 60% in the third year and increased by 90% in the fourth year. What was the cumulative change in sales over the 4 years? Penny Nom lui répond. 





Related rates 
20130217 

Ishaak pose la question : A hemispherical bowl is filled with water at a uniform rate. When the height of water is h cm the volume is π(rh^21/3 h^3 )cm^3, where r s the radius. Find the rate at which the water level is rising when it is half way to the top, given that r = 6 and the bowl fills in 1 minute. Penny Nom lui répond. 





How fast is the distance between the aircraft and the car increasing? 
20121024 

Steven pose la question : At a certain instant an aircraft flying due east at 240 miles per hour passes directly over a car traveling due southeast at 60 miles per hour on a straight, level road. If the aircraft is flying at an altitude of .5mile, how fast is the distance between the aircraft and the car increasing 36 seconds after the aircraft passes directly over the car? Penny Nom lui répond. 





Percentage change 
20120419 

Christine pose la question : For my intermediate macroeconomics class, there is a question about percent change.
The numbers are:
Quantities of oranges in 2010: 104
Quantities of oranges in 2009: 100
How would I calculate to find the percentage change in quantities? Penny Nom lui répond. 





The spread of a rumor 
20120409 

Roohi pose la question : The function f(t) = a/(1+3e^(bt)) has also been used to model the spread of a rumor. Suppose that a= 70 and b=3 0.2. Compute f(2), the percentage of the population that has heard the rumor after 2 hours. Compute f'(2) and describe what it represents. Compute lim t approaches infinity and describe what it represents. Penny Nom lui répond. 





The period T of a pendulum 
20120327 

Ashley pose la question : The period T of a pendulum is given in terms of its length, l, by T=2pi sqrt(l/g) where g is the acceleration due to gravity(a constant)
a. find dT/dl
b. what is the sign of dT/dl
c. what does the sign of dT/dl tell you about the period of the pendulums? Penny Nom lui répond. 





Water is flowing into a cup 
20111219 

Tim pose la question : A cup has a radius of 2" at the bottom and 6" on the top. It is 10" high. 4 Minutes ago, water started pouring at 10 cubic " per minute. How fast was the water level rising 4 minutes ago? How fast is the water level rising now? What will the rate be when the glass is full? Penny Nom lui répond. 





A cube of ice is melting 
20111205 

Emily pose la question : a cube of ice (i.e.) each side is of the same length) is melting at a rate such that the length of each side is decreasing at a rate of 5cm per hour. how fast is the volume of the cube decreasing (in cubic cm per hour) at the instant the length of each side is 25cm? Penny Nom lui répond. 





Water pouring into a conical tank 
20111121 

Patience pose la question : Hi my name is patience and I'm having a problem with this question.
Water pours into a conical tank of semi vertical angle 30 degrees at the rate of 4 cm^3/s, where h is the depth of the water at time t. At what rate is the water rising in the tank when h = 10 cm?
Thank you Penny Nom lui répond. 





A reservoir has the shape of an inverted cone 
20111003 

Roger pose la question : a reservoir has the shape of an inverted cone whose cross section is an equilateral triangle. if water is being pumped out of the reservoir at a rate of 2m^3/sec, at what rate is the depth of the water changing when the depth is 40 meters? Penny Nom lui répond. 





A hemispherical bowl with a lead ball inside 
20110927 

Jean pose la question : "(a) Water is being poured into a hemispherical bowl of radius 3 inch
at the rate of 1 inch^3/s. How fast is the water level rising when the
water is 1 inch deep ?
(b) In (a), suppose that the bowl contains a lead ball 2 inch in
diameter, and find how fast the water level is rising when the ball is
half submerged." Penny Nom lui répond. 





The height of a fluid in a horizontal tank 
20110724 

jason pose la question : Same set up as many others, cylindrical tank on its side, but I am interested in defining the change in volume and/or fluid level as a function of time at a constant volumetric outflow. I plan on hooking a pump to the tank so "gpms' will be constant. I have a couple different sized tanks and pumps so I want a general equation. Thanks for your help. Harley Weston lui répond. 





A conical container and a spherical balloon 
20110406 

Steven pose la question : Water is running out of a conical container 12 feet in diameter and 8 feet deep (vertex down) and filling a spherical balloon.
At the instant the depth of the water in the cone is 4 feet, the radius of the sphere is approximately 4 feet.
The rate of change of the depth of the water in the cone at the instant is approximately ______________ times the rate of change of the radius of the balloon. Penny Nom lui répond. 





Two ships 
20110405 

Gevork pose la question : Ship A is sailing due south at 16 mph. At the same time, a second ship B, 32 miles south of A, is sailing due east at 12 mph.
(a) at what rate are they approaching or separating at the end of one hour?
(b) At what rate are they approaching or separating at the end of two hours?
(c) When do they cease to approach each other and how far apart are they at that instant. Penny Nom lui répond. 





The rate of change of the area of a parallelogram 
20110405 

Gevork pose la question : Let a parallelogram have sides of 8 and 12 and let vertex angle A be decreasing at a rate of 2degrees per minute. Find the rate of change of the area of the parallelogram when angle A equals 30 degrees. Penny Nom lui répond. 





The rate of change of (8e^3x)+(27 e^3x) 
20101123 

Aleo pose la question : I am unable to solve this problem:
Find the rate of change of (8e^3x)+(27 e^3x), with respect to x when x= 0.5 Penny Nom lui répond. 





The distance between the origin and a moving point 
20100924 

Norma pose la question : I am having problems with this question
find the rate of change of the distance between the origin and a moving point on the graph of the function below if dx/dt=5 cm/sec
y=x^2+2 Penny Nom lui répond. 





A comparative report 
20100527 

jo pose la question :
Question from jo:
I have a comparative report and I was confused about how to get the percentage of the current 1st quarter vs. last year 1st quarter, vs. last year of the same month. I hope you could help me, thank you.
Example: Food sales: 3Day Sale Event
TY: 1,352,293.58 May (Back to School)
LY: 1,205,614.31 April (Summer Sale)
LY: 1,065,693.40 May 2009 Penny Nom lui répond. 





The rate of change of y with respect to x 
20100429 

Tom pose la question : I just had a quick calc question about wording that wasn't ever
addressed in class. When the book says "the rate of change of y with
respect to x", should it be considered how fast y is changing in
comparison to x?
I ask because the textbook says that "y is changing 3 times faster than x,
so the rate of change of y with respect to x is 3." I'm use to rate being
like velocity, as in units of distance per units of time. All we're told
in class is that it's the slope of the tangent line, I was hoping you
could clarify for me what exactly is meant by the wording of a "rate of
change of something with respect to something else". More specifically, what
"rate" and "with respect to" mean within this context?
Thanks for your time Harley Weston lui répond. 





Cooling 
20100307 

Lori pose la question : If a house is always at 20 degrees celsius.
Water (tea) boils at 100 degrees celsius.
5 minutes later the tea was 70 degrees celsius.
Use an equation to predict the temperature after 20 minutes. Tyler Wood lui répond. 





At what rate are the people moving apart? 
20091101 

saira pose la question : A man starts walking north at 4 ft/s from a point P. 5 minutes later a woman starts walking south at 5 ft/s from a point 500 ft due east of P. At what rate are the people moving apart 15 minute after the woman starts walking ? Harley Weston lui répond. 





Pennies, nickels and dimes 
20090922 

Kiadadh pose la question : Show 12 ways to come up with 28 cents using only pennies, nickles and dimes Robert Dawson lui répond. 





Percentage price change 
20090827 

alicia pose la question : what is the percentage price change between R66R10 if the answer between the two is R56 Penny Nom lui répond. 





Percentage decrease 
20090804 

Bill pose la question : How to calculate the Percentage Increase or Decrease of a $ value.
Example 
Site Spend for 01012008 thru 073108 was $ 3,465,660
Site Spend, 2009 YTD as of 073109, was $ 1,673,405
Site Spend down what % between these two amounts ? Penny Nom lui répond. 





Change 5/6 into a percent 
20090415 

Shelly pose la question : My question is when it says change 5/6 into a percent Penny Nom lui répond. 





The rate of change of the volume of a sphere 
20090325 

Kaylin pose la question : why the rate of change of volume of a sphere is not constant even though dr/dt is constant? Walter Whiteley lui répond. 





Related rates 
20090314 

Jeevitha pose la question : The side of an equilateral triangle decreases at the rate of 2 cm/s.
At what rate is the area decreasing when the area is 100cm^2? Stephen La Rocque lui répond. 





How fast is the visible surface of the earth decreasing? 
20090124 

Ray pose la question : A dive bomber loss altitude at a rate of 400 mph. How fast is the visible surface of the earth decreasing when the bomber is one mile high? Harley Weston lui répond. 





In the shadow of a flagpole 
20090122 

La pose la question : How fast is the length of the shadow of an 18 foot flagpole growing when the angle of elevation of the sun is 45 degrees and is decreasing at a rate of 10 degrees per hour? Harley Weston lui répond. 





Negative rate of change 
20090112 

hemanshu pose la question : when i have to find rate of change of decrease in any value my ans comes in negative why?????????? Penny Nom lui répond. 





Related rates 
20081126 

Lyudmyla pose la question : How fast is the volume of a cone increasing when the radius of its base is 2 cm and growing at a rate of 0.4 cm/s, and its height is 5 cm and growing at a rate of 0.1 cm/s? Harley Weston lui répond. 





How fast is the distance between the airplanes decreasing? 
20081110 

Crystal pose la question : At a certain instant, airplane A is flying a level course at 500 mph. At the same time, airplane B is straight above airplane A and flying at the rate of 700 mph. On a course that intercepts A's course at a point C that is 4 miles from B and 2 miles from A. At the instant in question, how fast is the distance between the airplanes decreasing? Harley Weston lui répond. 





Melting ice on a hemisphere 
20081020 

heather pose la question : The top of a silo is the shape of a hemishere of diameter 20 ft. if it is coated uniformly with a layer of ice, and if the thickness is decreasing at a rate of 1/4 in/hr, how fast is the volume of ice changing when the ice is 2 inches thick? Penny Nom lui répond. 





Related rates 
20081016 

Gisela pose la question : As sand leaks out of a hole in a container, it forms a conical pile whose
altitude is always the same as its radius. If the height of the pile is increasing
at a rate of 6 in/min, find the rate at which the sand is leaking out when the
altitude is 10in. Penny Nom lui répond. 





The rate of change of the volume of a cone 
20081015 

Barbara pose la question : Suppose that both the radius r and height h of a circular cone change at a rate of 2 cm/s.
How fast is the volume of the cone increasing when r = 10 and h = 20? Harley Weston lui répond. 





Bags of pennies 
20081011 

paul pose la question : jenny divided 15 pennies among 4 money bags.she could then pay any amount from 1p to 15p just by giving bags.how many pennies did jenny put in each bag? Penny Nom and Victoria West lui répond. 





The average rate of change of gasoline used 
20081006 

JHulie pose la question : What is the average rate of change of gasoline used, measured in miles per gallons
if you travel 212 miles, then you fill your gas tank up again and it takes 10.8 gallons.
If you designate your change in distance as 212 miles and your change in gallons as 10.8? Penny Nom lui répond. 





Vectors and an orientation change in the axes 
20080830 

moumita pose la question : what differences take place to a vector because of choice of orientation of the coordinate axes and why?? Harley Weston lui répond. 





Trough Filling with Water 
20080821 

lanny pose la question : a triangular trough is 10 feet long, 6 feet across the top, and 3 feet deep. if water flows at the rate of 12 cubic inches per minute, find how fast the surface is rising when the water is 6 inches deep. Janice Cotcher lui répond. 





Slope and rate of change 
20080623 

Lee pose la question : What is the difference between a slope and a rate of change? Stephen La Rocque lui répond. 





Percent improvement 
20080612 

JOHN pose la question : IF YOU HAD A RATE OF 678/HOUR AND YOUR NEW RATE/HOUR
IS NOW 1961 WHAT IS PERCENT OF IMPROVEMENT Penny Nom lui répond. 





The rate of change in the depth of the water 
20080612 

Liz pose la question : A rectangular pool 50ft long and 30ft. wide has a depth of 8 ft. for the first 20 ft. for its length and a depth of 3 ft. on the last 20ft. of its length and tapers linearly for the 10 ft in the middle of its length. the pool is being filled with water at the rate of 3ftcubed/ min
at what rate is the depth of the water in the pool increasing after 15 hours? Harley Weston lui répond. 





The average rate of change 
20080329 

Tom pose la question : For the function x/3x1 find the average rate of change between the interval x=1 and x=5? Harley Weston lui répond. 





Percentage savings 
20080201 

Donna pose la question : What is the percentage of savings if I bought an item for $98.60 that was $152.23 and something for $96.48 that was $136.65? Penny Nom lui répond. 





Percentage change 
20071219 

Aaron pose la question : I understand how figure percent of change and I can figure it on a calculator but if I have to do it without I'm not sure how to divide when the original amount is larger than the amount of change. For example, the decreased amount is 5.00 on 29.99, what would the percent be. Like I said I can do it on a calculator but need to know how to figure it without one. Penny Nom lui répond. 





Percent change between two value ranges 
20071128 

Joe pose la question : How do you calculate a percent change between tow value ranges  for instance if I project a range for 2007 to be between 100 and 120 and a range for 2008 to be between 120 and 140, how do I calculate the estimated increase between the range? Is it 0% to 40% (taking the two inside values rto calculate the minimum and the two outside values rto calculate the maximum?) Harley Weston lui répond. 





The rate of change of the concentration of a solution 
20071030 

Nicholas pose la question : A barrel initially has two kg of salt dissolved in twenty liters of water. If water flows in the rate of 0.4 liters per minute and the wellmixed salt water solution flow out at the same rate, how much salt is present after 8 minutes?
I tried working backwards given the answer but I can't seen to get their answer of ~1.7kg. Any help would be great! Thanks Harley Weston lui répond. 





The rate of change of the area of a triangle 
20071022 

Ahlee pose la question : So my question is:
The included angle of the two sides of a constant equal length s of an isosceles triangle is ϑ.
(a) Show that the area of the triangle is given by A=1/2s^2 sinϑ
(b) If ϑ is increasing at the rate of 1/2 radian per minute, find the rate of change of the area when ϑ=pi/6 and ϑ=pi/3.
(c) Explain why the rate of change of the area of a triangle is not constant even though dϑ/dt is constant Penny Nom lui répond. 





The average rate of change of a function 
20071011 

vern pose la question : Find the average rate of change of the function over the given interval. Compare this average rate of change with the instantaneous rates of change at the endpoints of the interval. f(X)=sinX for the inverval [0,pi/6]? Harley Weston lui répond. 





Percentage change 
20070821 

Saleena pose la question : Hiya, my name is Saleena and I'm studying business at college. My question for you is what is the percentage change of turnover of the following supermarket.
Turnover (Millions)  ASDA
2001 10,732
2002 12,188
2003 13,326
2004  14,318
2005 14,865 Penny Nom lui répond. 





The change in an average 
20070819 

farah pose la question : the average height of a group of 25 students goes up by 2 cm when astudent of height 165 cm replaces a student from the group.what is the height of the boy who went out of the group? Stephen La Rocque lui répond. 





Percentage change 
20070819 

nona pose la question : If inputs increase by 30% and outputs increase by 15%, what is the percentage change in productivity? Stephen La Rocque lui répond. 





Percentage change 
20070813 

Karen pose la question : I need a formula for calculating percentages in Excel. For example, we =
sold 4 units of an item one month, and 105 units the next. I need a =
formula to calculate the percentage increase in sales units. Also, if =
5251 were sold one month and 651 the next, what is the formula for =
calculating the percentage difference? Please help, thank you. Penny Nom lui répond. 





Buying and selling apples 
20070803 

Priya pose la question : Gorang bought 60 Kg of apples at Rs 48 per Kg. He sold 70% of the apples at Rs 60 per Kg and the remaining apples at Rs 35 per Kg.Find Gorang's gain or loss percent on the whole transaction. Stephen La Rocque lui répond. 





Percent change over multiple periods of time 
20070607 

Eric pose la question : I am trying to show the percent change over multiple periods of time.
Is there a formula for the percent change over multiple periods or will I have to calculate the percent change for each previous period versus the year prior? Penny Nom lui répond. 





Rate of change of distance between the clock hands 
20070605 

Jonathan pose la question : A certain Clock has a minute hand with a length of 4 inches long and an hour hand with a length of 3 inches long. How fast is the distance between tips of these hands changing at 9:00? Stephen La Rocque lui répond. 





Percent difference 
20070517 

Carolyn pose la question : What is the % difference between these two numbers 211373 & 185420 Gabriel Potter, Penny Nom and Steve La Rocque lui répond. 





Percentage change 
20070501 

katie pose la question : i no many people have asked about this but im still unsure what is percentage change i have my ks3 tomoro so please reply asap thankz Penny Nom lui répond. 





(ab)/b = c 
20070427 

Adam pose la question : What does
(ab)/b = c
represent when c is a percentage? Penny Nom lui répond. 





At what rate is the area of the triangle changing? 
20070224 

mac pose la question : two sticks 3.5 feet long are hinged together and are stood up to form an isosceles triangle with the floor. The sticks slide apart, and at the moment when the triangle is equilateral, the angle is increasing at the rate of 1/3 radian/sec. At what rate is the area of the triangle increasing or decreasing at that moment? Mac Penny Nom lui répond. 





A particle moving along a curve 
20061118 

Rachel pose la question : a particle is moving along the curve whose equation is: (xy^3)/(1+y^2)=8/5 assume the xcoordinate is increasing at the rate of 6 units per second when the particle is at the point (1,2). a. at what rate is the ycoordinate of the point changing at that instant? b. is the particle rising or falling at that instant? Penny Nom lui répond. 





An aircraft and a missile 
20061118 

Sarah pose la question : an aircraft is flying at a constant altitude with a constant speed of 600mph. an antiaircraft missile is fired on a straight line perpendicular to the flight path of the aircraft so that it will hit the aircraft at a point P. at that instant the aircraft is 2 miles from the impact point P the missile is 4 miles from P and flying at 1200 mph. at that instant, how rapidly is the distance between missile and aircraft decreasing? Stephen La Rocque lui répond. 





Wheat is poured on a conical pile 
20061117 

Rachel pose la question : wheat is poured through a chute at the rate of 10 cubic feet per minute and falls in a conical pile whose bottom radius is always half the altitude. how fast will the circumference of the base be increasing when the pile is 8 feet high? Penny Nom lui répond. 





The rate of change of the perimeter of a square 
20061107 

Karli pose la question : Find the rate of change of the perimeter of a square with respect to its area. Stephen La Rocque lui répond. 





A boat is being pulled towards a dock. 
20061106 

Cassie pose la question : A boat is being pulled towards a dock. If the rope is being pulled in at 3 feet per second, how fast is the distance between the dock and the boat decreasing when it is 30 feet from the dock? Penny Nom lui répond. 





Percentage differences 
20061023 

Michael pose la question : how do I calculate the percentage difference of a certain box size. for example. How much percent smaller is this box: 8.4mm x 6.3mm to this box: 9.35mm x 7mm Stephen La Rocque lui répond. 





How fast is the water level rising when the water is 1 meter deep? 
20061019 

Don pose la question : The cross section of a 5meter trough is an isosceles trapezoid with a 2meter lower base, a 3meter upper base and an altitude of 2 meters. Water is running into the trough at a rate of 1 cubic meter per minute. How fast is the water level rising when the water is 1 meter deep? Stephen La Rocque lui répond. 





Plotting percentage change 
20061011 

Beckie pose la question : I have worked out a set of percentage differences which are all percentage decrease. Should i express them as a negative percentage as 20%? I also need to plot them on a graph and am not sure whether to just use the percentage difference as it is, in which case i get a positive gradient, or include a negative axis and plot them in this way, in which case i would get a negative gradient. I think the slope of the curve will be the same either way so it might not matter! Penny lui répond. 





The velocity of a pendulum, part II 
20060907 

Erin pose la question : We saw the question in your database about the velocity of a pendulum swinging.....It is the same exact question....but there is another question......it says....
"estimate the instantaneous rate of change of d with respect to t when t = 1.5. At this time, is the pendulum moving toward or away from the wall? Explain." Harley Weston lui répond. 





Percentage weight change 
20060124 

Abdul pose la question : what is the percent change if a person's weight changed over 3 years:
year 1995 1997 1998 %change(19951998)
weight 63kg 67kg 73kg ......... Penny Nom lui répond. 





Percentage change when you start from zero 
20060102 

Joseph pose la question : I am not sure if my meaning for calculation for a percent change (CP/P)x100) is correct. In this case, C=10, P=0, does this mean 100 percent increase from previous period? Harley Weston lui répond. 





Percent change 
20051217 

Marie pose la question : What is the percentage change when 1500 becomes 2000? Penny Nom lui répond. 





Percentage increase 
20050919 

Dory pose la question : Last year sales was 120,000 $ and this year sales is 280,000 $, there was an increase in sales. what I would like to know is the percentage increase between the years with the formula. Penny Nom lui répond. 





Is this percentage change or percentage increase? 
20050815 

Betty pose la question : When calculating a percentage, if the formula is
A(new)  B(old)/A(new)
Is this percentage change or percentage increase? Penny Nom lui répond. 





Percent change 
20050701 

Betty pose la question : Can you tell me the difference between Percentage Change, Percentage Increase, Percentage Difference and please give an example of each, I am very visual. Penny Nom lui répond. 





A rate of change problem 
20041015 

Frank pose la question : Find the rate of change of the distance between the origin and a moving point on the graph of y = x(squared) + 1 if dx/dt = 2 centimeters per second. Penny Nom lui répond. 





Percentage change 
20040830 

Lauren pose la question : if egg A weighed 55.4g and after 2 days it weighed 60.9g how could i calculate the percentage change in weight? Penny Nom lui répond. 





Rate of change problems 
20040801 

Jim pose la question : I just want to check a couple average rate of change problems because i just guessed on how to do them. Can you tell me how to do them?
the question says if f(x) = sqrt(x + 3), find f( x + rx). I got sqrt( x + rx + 3)
the other two are : f(x)= 3x1 (f(x)  f(1)) / (x1) ... I GOT 3 &
f(x)= x^3  x (f(x)  f(1)) / (x1) ... I GOT x^2 + x Penny Nom lui répond. 





x^2/3  7 x^1/3 + 12 = 0 
20040405 

Jackie pose la question : I am having trouble solving this question for x:
1.) x^2/3  7 x^1/3 + 12 = 0 Penny Nom lui répond. 





x6square root of x +8=0 
20030510 

Elizabeth pose la question : x6square root of x +8=0 Penny Nom lui répond. 





Percentage change in completion rate 
20030221 

Remo pose la question : In the year 2000 300 out of a possible 600 completed a phone survey for a total of 50% completion rate. In the year 2001 20 out of 100 possible people completed the survey when it was redone. This is a completion rate of 20% To figure out the percentage change between the years can just use the difference between the percentage figures I already have? Or can I calculate it the same as you would for nonpercentage numbers. For example you gave an example here of a salary increase from $20 to $95 being an increase of 375%. Would I solve my problem the same way expect substituting my percentages (.5 and .2) in place of $20 and $95? Penny Nom lui répond. 





A penny, a nickel, a dime, a quarter, and a loonie 
20030121 

Blaine pose la question : I have 5 coins: a penny, a nickel, a dime, a quarter, and a loonie. How many different amounts of money could I pay using any combination of these coins? Penny Nom lui répond. 





Averages of Averages 
20021221 

Amy pose la question : If in the month of October the % of Payments Received was 80.74% and in November it decreased to 69.36%. Can you take the 80.7469.36/69.36 to get the % of difference. In otherwords can you take the % of difference when the numbers you are comparing are %'s???? Can you also take an average of an average? For example, average number of payments received in October was 25.00%, average number of payments received November was 50.00%, and the average number of payments received in December was 15.00%. Do you average (25.00%, 50.00% and 15.00%) or do you have to go back to the numbers that calculated the averages. For example, October 25.00% was based on 25 payments being received out of a possible 100. So instead of taking the average of the averages, do you take the average payments and the average customers over the 3 months and calculate the average??? Harley Weston lui répond. 





A spotlight shines on a wall 
20020525 

Barb pose la question : A spotlight on the ground shines on a wall 12m away. If a man 2m tall walks from the spotlight toward the bldg at a speed of 1.6 m/s, how fast is his shadow on the bldg decreasing when he is 4m from the bldg? Penny Nom lui répond. 





Conversion of units 
20020429 

Matt pose la question : I am having trouble finding a workable equation for the following problem, particularly the conversion of two systems of measurement. The question states that there are 27 grams of salt in a kilogram of seawater. And it asks how many tonnes (1 tonne = 1000 kilograms) of salt are there in one cubic kilometer of ocean. It also says that the density of seawater is 1.1 g/cm3. What is the equation and how do I figure out how many kilograms there are in a cubic kilometre? Harley Weston lui répond. 





Percentage difference 
20020308 

Tedd pose la question : Can you give me the formulas for calculating percentage differences between two numbers? For example: if the first number is 10 and the second number is 15, then the second number is 50% larger than the first number. However, the formula to calculate that percentage won't work if the first number is greater than the second number as in the following example: The first number is 15 and the second number is 10, with the second number being 33.3% less than the first number. Or maybe I'm mistaken and the same formula will work in both situations. Penny Nom lui répond. 





Why do you flip the inequality sign? 
20011026 

Sean pose la question : I have a question about an inequality problem. Here it is: Solve and graph 5  3x => 17. (=> is greater than or equal). Please tell me why you flip the inequality sign when divinding by a negative number. Penny Nom lui répond. 





How far does the fly fly? 
20010807 

Harold pose la question :
6 MPH 4 MPH
Rachel  Eli
10 Miles apart
The fly is on Rachels handlebars. The fly is scared so it flys back and forth at 20 MP H. How far has the fly flown when Rachel and Eli meet? f Penny Nom lui répond. 





Jim's poker game 
20010524 

Nick and Karnal pose la question : One day jim played poker with some of his friends and lost half his money.the number of dollars he had before the game was the same as the number of cents he had after the game, and the no of cents he had before the game was twice as much as the number of dollars he had after the game.how much money did he have before thegame???
Later that day jim met a friend Al on the street."hi al!Do u have any change on you al?""yes" "Good!can u give me a change of a dollar?" "I am afraid not!" "Then give me change of 50 cents.""I am sorry i cant." "how about a change of a quarter?""not possible." "a dime." "also not" "a nickel?" "not even that."
al had no bills or silver dollars on him.whats the largest amount of cash he could have had? hope u can help me. Penny Nom lui répond. 





Coins and monomials 
20010304 

A student pose la question : Tokola has 5 coins with a total value of $1.05. He canot make change for a dollar, 5 cents, 10 cents, 25 cent, or 50 cents. What 5 coins does he have? and Determine whether 6cd is a monmial. Explain why or why not. Penny Nom lui répond. 





Velocity of a pendulum 
20000828 

Mekca pose la question : A pendulum hangs from the ceiling. as the pendulum swings, its distance,d cm, form one wall of the room depends on the number of seconds,t, since it was set in motion. assume that the equation for d as a function of t is: d=80+30cos3.14/3t, t>0. estimate the instantaneous rate of change of d at t=5 by finding the average rates for t=5 to 5.1, t=5 to 5.01, and t=5 to 5.001. Harley Weston lui répond. 





Change for a dollar 
20000216 

Rachelle pose la question : What is the least positive number of coins that is impossible to give out change for a dollar? It is higher than 50 i know and you can us dimes, nickels, pennies, quarters, 50 cent pieaces and silver dollars. Claude Tardif lui répond. 





Play ball 
20000203 

Jessie pose la question : Here's a calc question that is probably a lot easier than I am making it. If you have a legendary "baseball problem" for the related rates section of Calc I, and you are given that the runner is running from 2nd to 3rd base at a given rate, and the umpire is standing at home plate, and you are given the distance between the bases on the field, how do you find the rate of change of the angle between the third base line (from the point of the umpire) and the runner? Here is a sample prob: Runner is moving from 2nd to 3rd base at a rate of 24 feet per second. Distance between the bases is 90 feet. What is the rate of change for the angle (theta, as described previously) when the runner is 30 feet from 3rd base? Harley Weston lui répond. 





Percentage change 
19991208 

Michael Weinberg pose la question : I am the Laboratory information system supervisor in a hospital. Our computer system calculates the change of specific results to monitor a patient's status. But there is a problem with the calculation in the base code of the program. If one day the patient has a Blood count of 100 (P for Previous) then the next day the Blood count is 75 (C for current), the computer should calculate the change as 25% using the calculation PC/P= D (D for Delta) and then check for positive or negative by the equation If P>C then D*1 or If P The program is calculating using the equation: ((P/C)1)*100 in the above situation this would calculate the Delta as 33.33333% Referenced in a Laboratory manual published before computers were used to calculate the delta changes. . . . Penny Nom lui répond. 





Percentage increase 
19991003 

Ann Allen pose la question : I am a a student in the 12th grade. I need to know how to calclulate the following: A percentage increase from 2.0% to 9.5% is what percentage? Harley Weston lui répond. 





The average rate of change of a function 
19990420 

Tammy pose la question : Suppose that the average rate of change of a function f over the interval from x=3 to x=3+h is given by 5e^h4cos(2h). what is f'(3)? I would appreciate any help with this question. Harley Weston lui répond. 

