







Matrice 
20060201 

Kader pose la question : mon probleme est le suivant soit deux matrices carrees A et B d'ordre n qui sont anticommutatives AB= BA , demontrer que au moins une des deux matrices n'est pas inversible si n est impair.
je n'arrive pas a utiliser le fait que n soit impair, trouver le rapport entre n impair et inverse des matrices, je pars sur la base de DETAB=DETA*DETB Claude Tardif lui répond. 





probleme de matrice 
20060201 

Un eleve pose la question : mon probleme est le suivant soit deux matrices carrees A et B d'ordre n qui sont anticommutatives AB= BA , demontrer que au moins une des deux matrices n'est pas inversible si n est impair. Claude Tardif lui répond. 





La bissectrice de l'angle ABC 
20000216 

Laurent Gauthier pose la question : Estce redondant d'ecrire "angle ABC" avec un accent circonflexe sur le B? Peuton ou devraiton se contenter d'ecrire soit ABC (avec l'accent), soit l'angle ABC (sans accent) ? Le contexte dans lequel ceci apparait est le syntagme "la bissectrice de l'angle ABC", c'estadire que je me demande si on devrait ecrire "la bissectrice ABC " (avec accent), "la bissectrice de l'angle ABC" (sans accent) ou "la bissectrice de l'angle ABC" (avec accent). Claude Tardif lui répond. 





30 % off 
20210907 

Corrine pose la question : When I am shopping for clothing that is for sale, the advertisement may say the item is 30% off. The original price was $70. How much would it now be? (how do I figure that out?) Thank you! Penny Nom lui répond. 





What was the original price? 
20200201 

Gracie pose la question : If you buy something for $6.30 and it’s 30%off what was the original price? Penny Nom lui répond. 





What is the original price? 
20190515 

Tyler pose la question : if 45% of an item is $90.00, then what is the original price Penny Nom lui répond. 





80% of an item is $200.00 80% of an item is $200.00 
20190425 

kayla pose la question : if 80% of a item is $200.00 what is the original price Penny Nom lui répond. 





Margin with commission as part of selling price 
20190213 

Anni pose la question : I need to find selling price to put us at 24% margin.
15% commission is based on selling price and is included in our cost.
I'm trying to do it excel and keep getting a circular reference.
Total cost= cost + commission (15% of selling price)
Selling price=total cost + 24% margin Penny Nom lui répond. 





Sale price and employee discount 
20190118 

Margaret pose la question : What is the formula to find the
75% off full price item that was already marked 30% off? Penny Nom lui répond. 





Price before VAT and a discount 
20181115 

Carol pose la question : I bought a computer for £330.
The selling price included VAT at 20%.
Then I was allowed a staff discount of £30.
What was it’s original price before the VAT and staff discount? Penny Nom lui répond. 





The price of eggs rises 10 cents per dozen 
20181110 

Maddie pose la question : Hi! I'm currently struggling with a word problem that says:
"If the price of eggs rises 10 cents per dozen, one will be able to get 2 dozen fewer eggs with $6.00 than was possible at the lower price. What is the lower price?
We are working on completing the square and all of the problems I've done so far in this chapter require using that method. If possible and needed, could you explain how to set up the equation?
Thank you so much! I appreciate all your help!! Penny Nom lui répond. 





The price of a sheet of metal 
20180402 

Nydia pose la question : What is the formula to calculate the following:
I nee to find out what the sheet price be. The dimensions are 2000x3000 mm into ft they are 78x1181.
The sqft price I have is $22.16. How do I figure out the sheet price from that? Penny Nom lui répond. 





An item on sale costs 55% of the original price. 
20180228 

Debra pose la question : An item on sale costs
55%
of the original price. The original price was
$51
. Penny Nom lui répond. 





The wholesale price given the retail price and the markup 
20180207 

Matthew pose la question : Retail $99
Markup is 80%
What is the equation to find the original (wholesale) price (55)?
thanks Penny Nom lui répond. 





Average price 
20170915 

Annette pose la question : If I sold a widget at $15.50 17.5% of the time and $16.50 88.5% of the time what is the algebraic expression for that. How do I arrive at an average price Penny Nom lui répond. 





What is the regular price? 
20170511 

Saira pose la question : If the sale price is 55.50$ and the discount is 12% what is the regular price Penny Nom lui répond. 





Selling price and markup 
20170424 

Julie pose la question : What would the cost of an item be, if the sell price was $50 and the markup 48% Penny Nom lui répond. 





How do I establish the original List Price? 
20170115 

Bob pose la question : (1) I have a net price item at $4,664.66 but do not have the discount percentage. I have been told I received 40%? How do I establish the original List Price and to confirm what discount I received? Penny Nom lui répond. 





Selina saved $6 on a 20% off sale 
20161014 

Myra pose la question : I don't know how to help my child answer this question  Selina bought a shirt on sale that was 20% less than the original price. The original price was $6 more than the sale price. What was the original price? Penny Nom lui répond. 





A 15% discount 
20160809 

eunice pose la question : brian brought a printer sale at the store. the discount was 15%, and brian saved 550. what was the printer original price? Penny Nom lui répond. 





A 70% off sale 
20160511 

virginia pose la question : If the sale price is $129.99 @ 70% off  what was the original price? Penny Nom lui répond. 





The original price before a discount and taxes 
20151209 

Michelle pose la question : Good day,
I would like to know if there is a particular equation to validate the following information:
I had to find the original cost of an item sold for 759.36$ before a 25% discount and 13% taxes.
I know we must use separate question to obtain the answer but I am unsure how to write the equation to validate my answer. Penny Nom lui répond. 





Two price reductions and a coupon 
20150916 

Suszanne pose la question : Mary purchased an item for 45% off the original price, plus an additional 20% off the sale price.She also had a $5 off coupon, which the salesclerk applied after these two discounts. Mary's final purchase price for the item was $50. She paid no sales tax, what was the original price of the item? Penny Nom lui répond. 





What is our cost? 
20150127 

Johanna pose la question : I have a pieces of 3/4" sch40 (round tube) 240" long at $70. What is our cost. We also add 35% to our cost for selling price. How do I figure this out? Penny Nom lui répond. 





Selling items at a reduced price 
20150109 

Kent pose la question : I have an item I sell for $19.95 and make a profit of $10.97 for each sale.
If I reduce the price to $14.97, my profit is $5.99 each sale.
Is there a formula to determine how many more I would need to sell
at $5.99 per sale to make the same net cash (profit) as selling at $10.97 per sale? Penny Nom lui répond. 





A price increase and a consumption decrease 
20140816 

sujan pose la question : If the price of petrol increases by 25% and Rajesh intends to spend only 15% more on petrol then by how much % should he reduce the quantity of petrol he buys? Penny Nom lui répond. 





What was the selling price? 
20140425 

Con pose la question : Apple built 40 32GB wifi iPads, gave away two in a contest, and sold the rest at two times the manufacturing price. If the company's total profit was $10,782, what is the selling price of one of these iPads? Penny Nom lui répond. 





Determine the selling price 
20140308 

augustine pose la question : knowing an auctioneer charges a 7% fee and I know I want $74,400 what is the formula to determine selling price. Penny Nom lui répond. 





Finding the retail price 
20140222 

Judy pose la question : An item is currently on sale at 37% off the retail price. The item now sells for $350.
My Question:
What is the retail price and what is the formula or steps to figuring that out? Penny Nom lui répond. 





A sale price for a TV 
20131128 

tom pose la question : a TV can be purchased for $278 normally is $328. what is the percent of the present cost of this TV will you be saving? Penny Nom lui répond. 





Matrices 
20131110 

Ricky pose la question : Why must we have brackets around matrices. Why don't we just neatly write an array of entries crosswise and up and down to indicate a particular matrix? Chris Fisher lui répond. 





Price, revenue and profit 
20130922 

lorraine pose la question : What price maximizes revenue? What price maximizes profit?
The only data I'm given is total output, total revenue, and total cost.
I'm not sure how to set up a formula Penny Nom lui répond. 





What is the original price? 
20130425 

Dylan pose la question : shirts on sale for 25% off, the sale price is 12.75. What is the original price? Penny Nom lui répond. 





Markup and discount to get a sale price 
20130302 

Warren pose la question :
If you are an ardent shopper you will be aware of the discount (% decrease) marketing strategy to produce the sale price. I began to wonder just how much markup (% increase) was added initially to an item in order to deliver the discounted sale price.
It was simple to construct a formula to convert one to the other.
For example a 30% (mark down) decrease in price required a 42.86% (mark up) to increase the price initially to Tag price. However when I started apply the formulae to a number of circumstances I noticed some very interesting circumstances associated with this relationship
For example a 99.999999% decrease is numerically equal to a 9,999,999,925% increase (huge ratio difference) while conversely a 0.1% decrease is numerically equal to a 0.10010010% increase (Infinitesimally small ratio difference) so the patterns appears logarithmic not linear.
However what really caught my attention was this pattern
See http://www.ozsmart.com/doc/percentage.htm
My questions is why does the decline in the ratio of increases in required mark up (%) price peak at 50 and 51% precisely and then expand again as the percentage move higher
Any explanation would be appreciated Harley Weston lui répond. 





Your profit should be 20% of your cost 
20130221 

anis pose la question : if the customer says your profit should be 20% of your cost..
1) my selling value should be cost +20% of cost = SP
or
2)cost / 0.80 = SP which is correct...if the second answer is right how should i justify my customer Penny Nom lui répond. 





What is the better price? 
20120330 

john pose la question : What is the better price?
If a bag of mulch sells for $6.75 and contains 2.7 cubit feet versus a bag selling for $5.99 and contains 2 cubit feet.
Which is the better value? Penny Nom lui répond. 





The price per square inch of a pizza 
20120317 

jordan pose la question : pizzaz pizza sells a small pizza for $10.99.it has a diameter 10 inches.what is th price per square inch ? Penny Nom lui répond. 





What was the cost price of the article? 
20111110 

tashana pose la question : By selling an article for $320,the profit was 20% of the cost price.what was the cost price of the article. Penny Nom lui répond. 





Geocaching 
20101015 

Clint pose la question : I am stuck on a puzzle for Geocaching which is a GPS game.
I know it is a number matrix but don't know how to start.
[1 7 16 3 9; 1 3 18 20 33] x [1 8 9 3 5; 0 1 0 4 2; 0 0 1 2 1; 0 0 0 1 1; 0 0 0 0 1] = ? Stephen La Rocque lui répond. 





Selling price, cost and profit 
20100622 

Alex pose la question : The profit on a certain television set is 16.5% of the cost price. If the profit is $330,
Find:
a) the cost price
b)the selling price of the television Penny Nom lui répond. 





The price before tax 
20100215 

dawn pose la question : the sale tax on a cape was 6%,and total price with tax was $92.75,what was the price of the cape? Penny Nom lui répond. 





Find the original price 
20091106 

Cyndy pose la question : Find the original price of a pair of shoes if the sale price is $98.00 after a 30% discount. Penny Nom lui répond. 





Commodity price increase 
20091104 

bharat pose la question : if price of a commodity increases by x% the to keep the expenditure same
the decrease in consumption should be (x/(x+100))*100, why? Penny Nom lui répond. 





A trillion grains of rice 
20090914 

akaila pose la question : can 1trillion rice grains fit in a classroom with the area of 144.4m3 Penny Nom lui répond. 





Price increases and decreases 
20090902 

craig pose la question : I work for an industry that bases it price increases and decreases on commodity pricing  Customer get confused on how/why we calculated new prices due to movement in the market 
Price go up x% for every $10 of movement in the market 
For this example
Movement went down by $30 and it is 2% for every $10  so price decrease was 6%.
Customer's price is currently $100.
We say  $100/1.06= new price of $94.3
Customer says  $100*.94= new price of $94.
They don't understand that if board went back up $30 which would be 6% increase, they wouldn't be back at $100 if they multiplied on the price decrease.
$94*1.06=$99.64 vs. $94.3*1.06=$100 (Back to the original price)
What is the best way to explain to customer besides using this example?
Any help or info is appreciated.
Craig Victoria West 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. 





Torricelli's trumpet 
20090729 

Gary pose la question : I was reading about torricelli's trumpet which is described by the equation1/x which is then rotated around the x axis which results in a figure which looks like a trumpet. Now in order to find the volume the integral 1/x^2 dx is used which diverges when integrated so the volume is finite.However if you integrate 1/x dx which is the formula on the plane the answer diverges. Now if you took an infinite area then rotated it around the x axis shouldn't you get an infinite volume? Notice the area I am talking about is under the line 1/x not the surface area of the trumpet which is what the painters paradox is about What am I missing? Thanks Robert Dawson lui répond. 





The retail price for an ice cream scoop 
20090705 

Patricia pose la question : Hi  I am trying to figure out the fairest retail price for an ice cream scoop. We have an ice cream parlor
and the cost of the ice cream we buy by the bulk container has recently been increased so now we must charge
more for our scoops. We pay a wholesale price of $25.40 for 242 ounces of ice cream. The cost per ounce is
$0.105. What is the formula for figuring out how much to charge retail per scoop? This is probably so simple
but confusing to me. Please help. Thank you! Harley Weston lui répond. 





Unit Price 
20090608 

MATTHEW pose la question : Question from Matt:
I quoted my customer $112.50 per 1,000 sheets per linear yards. My client said I was to high. I need to be at 18 cents per square inch. If I matched his 18 cents per square ines what would my linear yards per 1,000 sheets price be? It comes on a 12.5 inch roll. Janice Cotcher lui répond. 





Grain of rice on a chess board 
20090330 

andy pose la question : Is there an easy way for my students to find out 8 to the power of 21 to solve the grains of rice doubling investigation on a chessboard? Any suggestions welcome. Thanks very much Robert Dawson and Claude Tardif lui répond. 





Find the retail price 
20090318 

Allie pose la question : If you have food that costs $0.75 per portion and your food cost is 16.5% how would you find the retail price? Penny Nom lui répond. 





The column space of a matrix 
20090212 

John pose la question : Question from John, a student:
A=
1 1 0 0
1 1 0 0
0 0 1 0
0 0 1 1
B=
1 5 6
1 5 6
0 7 2
0 0 9
Is the space spanned by the columns of A the same as the space spanned by the columns of B? Harley Weston lui répond. 





Calculating markup 
20090203 

Tonya pose la question : I'm trying to figure out the formula for the following, I have a product that I want to receive a certain profit, but with this product I also have to pay a percentage of commission to someone. I need to know how to calculate my new selling price taking into account the markup percentage, but I don't want my cut to be lowered. I have calculated the markup percentage to get my new selling price with the commission, but it lowers my cut once I pay the commission and I don't want it to do that. Thanks Penny Nom lui répond. 





PST and GST 
20090120 

janet pose la question : Hello
I need to figure what one would pay pst 8% gst 5% on a total of $1700.00
I have a small business some pay with cash I need to calculate the taxes in reverse Can you help with formula that the government might like
Thank you
Janet Harley Weston lui répond. 





A price reduction and a discount 
20080911 

Rita pose la question : A store advertises that during its Labor Day sale $15 will be deducted from every purchase over $100. In addition, after the deduction is taken, the store offers an earlybird discount of 20% to any person who makes a purchase before 10 a.m. If Hakeem makes a purchase of x dollars,
x > 100, at 8 a.m., what, in terms of x, is the cost of Hakeem's purchase?
(1) 0.20x  15 (3) 0.85x  20
(2) 0.20x 3 (4) 0.80x  12 Penny Nom lui répond. 





The selling price 
20080904 

Robert pose la question : Client wants to sell his property providing he is left with 100000.00$ net.
How do I calculate selling price if commission is 6% and taxes on the commission 6% Fed and 7.5%prov.
I'm taking the real estate class and this one really got me. Penny Nom lui répond. 





A linear system 
20080823 

dipesh pose la question : consider the system of equations
x6y+2z=5
2x9yz=14
4x+12y3z=19 by reducing the augm matrix to row echelon form, find
the solution to the equation.
leaving the first two equations the third is changed to 3x+6y+14z=31
show the equations have infinitely many solutions and give a general
formula for them Penny Nom lui répond. 





What is the GST component? 
20080611 

Jilly pose la question : I need to find a quick and easy formula for finding the gst (10%) of the total amount in $ terms, eg: the total is $500 what is the gst component? Penny Nom lui répond. 





Calculating a price based on markup 
20080603 

Sheldon pose la question : I know the most common form for retail businesses of calculating a price based on markup is:
Cost/(1  Markup), but how is this supposed to work for a business that desires a markup of over 100%. Harley Weston lui répond. 





Selling price 
20080510 

Roxane pose la question : I'm trying to figure out the formula for the following, I have a product that
I want to receive a certain profit margin, but with this product I also have
to pay a percentage of commission to someone. I need to know how to
calculate my new selling price taking into account the markup percentage, but
I don't want my gross margin to be lowered. I have calculated the markup
percentage to get my new selling price with the commission, but it lowers
my profit margin once I pay the commission and I don't want it to do that. Penny Nom lui répond. 





Determinants 
20080502 

Henry pose la question : I have a question about solving 3x3 matrices.
The traditional way, or at least the way I've been taught, is that if one has a 3x3 matrix such as:
[ a b c ]
[ d e f ]
[ g h i ]
one solves it according to this formula:
[ei  hf)  (bi  hc) + (bf  ec) = determinant.
According to a book I'm now studying to prepare for the California CSET exam, there is another, easier, way to solve it:
[ a b c ] [ a b ]
[ d e f ] [ d e ]
[ g h i ] [ g h ]
In other words, one repeats the first two rows of the matrix and adds them to the right.
At this point, the determinant is calculated thus:
(aei) +(bfg) + (cdh)  (gec)  (hfa)  (idb).
Is this, in fact, correct? Harley Weston lui répond. 





Matrix multiplication 
20080408 

manashi pose la question : i. why matrix division is not possible?
ii.when we add or subtract two matrix , getting the result by addind or subtracting correspondind elements....but in case of multiplication it is not but why? Harley Weston lui répond. 





Actural cost, selling price and commission 
20080221 

LiSa pose la question : I have a question about a few things if anyone can answer...
ex.
actual cost (AC) = $1000
selling price (SP) = $
amount earned for company (C) = 15% of... selling price?
commission 1 (C1) = 2.5%
commission 2 (C2) = 2.5%
How would you calculate how much the company's commission amount would be as well as the amounts for the other 2 that get 2.5%? And what would the selling price be? (the 15% $ + 2.5% $ + 2.5% $ ?)
Is the 2.5% taken from the original amount? I am soooo confused!
If anyone could help, that would be great! Harley Weston lui répond. 





The best price for topsoil 
20071115 

Dawn pose la question : What is a better deal for topsoil, $150.00 for 10 cubic yards, $170.00 for 22 tons, or $200.00 for 11.5 yards? Penny Nom lui répond. 





Twenty dining tables 
20070813 

priya pose la question : Utkarsh bought 20 dining tables for Rs 120000 and sold these at a profit equal to the S.P of 4 dining tables.Find the S.P of one dining table.(give the answer in statements) Stephen La Rocque lui répond. 





Discount percentage 
20070711 

Greg pose la question : List Price: $50.00
Discount: 33 1/3%
What would the net price be? Stephen La Rocque lui répond. 





A margin of 19% 
20070201 

Ed pose la question : I PAY $10.95 FOR THIS PRODUCT, HOW SHOULD I PRICE IT IN ORDER TO HAVE A MARGIN OF 19% COST. Penny Nom lui répond. 





What is the original cost? 
20060419 

Charlie pose la question : Selling a piece of furniture for $670 and the profit is 35%. What is the original cost? Stephen La Rocque lui répond. 





What is the cost price? 
20060414 

Purushotham pose la question : If the selling price is 120 and the profit is 20%, what is the cost price? Stephen La Rocque lui répond. 





Price percentages 
20060413 

Kristine pose la question : An item that is no longer on sale at "25% off" receives a price tag that is 33 1/3% more than the sale price. Has the item price been restored to its original price? Why or Why not? Stephen La Rocque lui répond. 





List price plus 10% 
20060403 

Heather pose la question : We shipped 2 pieces of an item with a unit price of $578.74 for a total amount of $1157.48. My task is to bill the customer at LIST + 10%. What formula do I need to use to calculate this? penny Nom lui répond. 





Who is taller: John or Mary? 
20050914 

Ulises pose la question : All the students in a school are arranged in a rectangular array. After that, the tallest student in each row was chosen, and then among these John Smith happened to be the shortest.Then, in each column, the shortest student was chosen, and Mary Brown was the tallest of these. Who is taller: John or Mary? Penny Nom and Claude Tardif lui répond. 





Cost price 
20050525 

Sunitha pose la question : What is (how to calculate) the cost price of a product which is markedup by 15% and retailed at $25? Penny Nom lui répond. 





A matrix problem 
20050404 

Alan pose la question :
Let A = 

1  1  0 

2  1  2 
a  b  c 
where a, b, c are constant real numbers. For what values of a, b, c is A invertible? [Hint: Your answer should be an equation in a, b, c which satisfied if and only if A is invertible.]
Judi McDonald lui répond. 





Two matrix problems 
20050330 

Sue pose la question : Question 1
Suppose all matrices in the equation below are square and invertible. Solve for x .
BA1XB1 + 2BA + In = 0 (the symbol "0" here denotes the matrix of all 0's in it)
Also, A1 or B1 is indicating inverse and "In" = for example, A1 times A
I hope you understand the above. I have to show all the steps.
Question 2
Suppose we consider the set of all 2x2 matrices along with the operations of matrix addition and multiplication. Do they form a field? Why or why not?
I think the answer is no because under multiplication it is not commutative and not all square matrices are invertible. I not positive so I'd like some help. Penny Nom lui répond. 





A matrix construction problem 
20050314 

Marcelo pose la question : I want to know if is it possible to solve this problem:
I have an empty NxM matrix and I know totals (sum) by rows and totals by column.
Is there any algorithm to fill the matrix so that the summary of columns and rows gives the original values I have? Harley Weston lui répond. 





The price of a book 
20040918 

Dorly pose la question : If the number of toonies required to buy a book is nine more than the number of
fivedollar bills required to buy the same book, determine the cost of the book. Penny lui répond. 





Arrays 
20040219 

A parent pose la question : please demonstrate mathematical arrays fro a 3rd grader Penny Nom lui répond. 





Matrices 
20031205 

Julie pose la question : I am doing a project and need to find some mathematiciens who had an influence in matrices. I can't seem to find any when I search online. Could you please help me with this? Judi McDonald lui répond. 





The mean house price 
20030910 

Carol pose la question :
Question: I have to find the mean from the following example: Price Range £000  No of Houses  55 and under 60  3  60 and under 65  6  65 and under 70  13  70 and under 80  21  80 and under 100  15  100 and under 130  7  130 upwards  1  I know when calculating the mean you use the mid points of the classes, but how does this work for the 130 upwards class? Also, does this still work given the difference in the classes (ie. 1st class is 5, 5th class is 20, etc). Any help to get me started would be greatly appreciated. Penny Nom lui répond. 





An onsale DVD player 
20030709 

Kim pose la question : I have a DVD player with a regular selling price of $175 and percentage of discount is 10 percent. How to solve for discount amount and sale price? Also, when you figure out the sale price how to figure out commission amount when percentage of commission is 5 percent? Penny Nom lui répond. 





A determinant 
20030213 

A student pose la question :
I have to find the determinant of the following matrix 2  3  1  2  4  3  0  2  5  1  4  2  1  3  5  2  3  4  1  2  6  0  3  2  4  Penny Nom lui répond. 





A house's selling price 
20021105 

Tanisha pose la question : a CERTAIN REALESTATE AGENT RECEIVES $6 FOR EVERY $100 OF A HOUSE'S SELLING PRICE. HOW MUCH WAS A HOUSE SOLD FOR IF THE AGENT $10,725._ Penny Nom lui répond. 





A sale price 
20021015 

Chester pose la question : A jacket is on sale for 32% off. Find the original if the sale price is $89.00 Penny Nom lui répond. 





A sale on eggs 
20020117 

A student pose la question : A store had a sale on eggs, selling 13 eggs for the usual price of a dozen eggs. As a result, the price of the eggs was reduced by 4 cents a dozen. What is the original price for a dozen eggs? Penny Nom lui répond. 





Matrix 
20011121 

Hoda pose la question : I have a question about matrix multiplication; well, actually, matrix division. I am assuming that matrices are divided the same as they are multiplied; that is, row by column. But what happens if you have to divide by zero? How does this affect the resulting matrix? Patrick Maidorn and Penny Nom lui répond. 





Conformable matrices 
20010805 

Wayne pose la question : Can someone explain the concept of conformable matrices in a way that is easy to understand ? One definition says to multiply matrices rows and columns must conform, ie, 5 x 3 matrix times a 3 x 5 matrix. In the next example, however a 8 x 1 matrix and a 8 x 3 matrix are said to be conformable! Steve Kirkland lui répond. 





Matrix reconstruction 
20010719 

Guy pose la question : Is there a way to get the sums of rows, columns and diagonals of an n x n matrix to reconstruct the original matrix? Walter Whiteley and Patrick Maidorn lui répond. 





Oil revenue 
20010421 

Brian pose la question : Suppose that t months from now an oil well will be producing crude oil at the rate of r(t), not a constant, barrels per month and that the price of crude oil will be p(t), not a constant, dollars per barrel. Assume that the oil is sold as soon as it is extracted from the ground.  Find an expression for the total revenue from the oil well, R(t).
 A certain oil well that currently yields 400 barrels of crude oil a month will run dry in 2 years. The price of crude oil is currently $18 per barrel and is expected to rise at a constant rate of 3 cents per barrel per month. What will be the total revenue from this well? {Hint: Model the degraded production rate with the equation:
r(t) = (ABt)e^{0.04t}} Harley Weston lui répond. 





Matrices 
20010326 

Peg pose la question : What are some applications of matrices, basic trigonometry, and linear systems in the real world? I'm writing and Algebra report about where these topics are used outside of the classroom. Judi McDonald and Walter Whiteley lui répond. 





Solving Equations 
20010223 

Stephanie pose la question : Do you know who came up with solving equations? Do you have any websites that can give me good information on solving equations? Do you know any history on solving equations? Do you know what solving equations is used for? And finally............Sorry about all of the questions :) Has the form of solving equations changed from the time it came out to now? Juci McDonald lui répond. 





The city transit system 
20010107 

Jacky pose la question : The city transit system carries an average of 9450 bus riders a day, for a fare of $1.75 each. The city wants to reduce car pollution by increasing ridership and to maximize the transit system's revenue at the same time. A survey indicates that the number of riders will increase by 150 for every $0.05 decrease in fare. Harley Weston lui répond. 





Where will we use this in the real world? 
20001011 

Jane Ann Musgrove pose la question : As a teacher of mathematics, I am always asked "Where will we use this in the real world?". I am seeking ideas/sites via the internet where students can find answers to this type of question. Can you help me? To be more specific, right now I am interested in finding careers where the employees would use the concepts of "Radicals", "Matrices", and "Logarithms". This information will be used by students to make presentations to the class on their findings from internet searches. Harley Weston lui répond. 





A matrix equation 
20000514 

A student pose la question : Right now, we are dealing with matrices and we are supposed to solve the following problem on our graphingcalculators: 2a+3b4c+d=20 a2b+3c5d=14 3a+4b2c+3d=19 5ab+6c+4d=5 Penny Nom lui répond. 





Matrices Information 
20000502 

William Avery pose la question : I am an OAC student at Governor Simcoe Secondary School in St. Catharines Ontario. Today at school we were handed an independent study project by our Finite teacher. This assignment is based on Matrices, it involves performing some simple matrix calculations, but also involves a written section. This written section asks for the following: . . . Marley Weston lui répond. 





Taxis in Chicago 
20000327 

A high school studenthigh school student pose la question : Suppose that taxis pick up and deliver passengers in Chicago, which is divided into three zones. Records kept by the drivers show that of the passengers picked up in Zone 1, 50% are taken to a destination in Zone 1, 40% to Zone 2, and 10% to Zone 3. OF the passengers picked up in Zone 2, 40% go to Zone 1, 30% to Zone 2, and 30% to Zone 3. Of the passengers picked up in Zone 3, 20% go to Zone 1, 60% to Zone 2 and 20% to Zone 3. Suppose that at the beginning of the day, 600 of the taxis are in Zone 1, 100 in Zone 2, and 300 in Zone 3. What is the distribution of taxis in the various zones after all have had two riders? Harley Weston lui répond. 





Matricies 
19981126 

Stephanie Webster pose la question : If a matrix for a rectangle looks this way: AACC BDDB What does the matrix for a square look like? Penny Nom lui répond. 





Mathematical Arrays 
19980501 

Gene Lanctot pose la question : Could someone please explain what a mathematical or arithmetical array is? The array in question is used in grade three math in Ontario. I would also like to know what its purpose is. Harley Weston lui répond. 





Matrices 
19980310 

Ksya pose la question :
 A and B are matrices. If A^n=B^n, can we say A=B or det(A)=det(B) or det(A)^n=det(B)^n ? Any conditions ???
 If B^(1) is the inverse of B, where B is a matrices. Can we say [(B^(1))^n][B^n]=I, where I is identity matrices? Any conditions???
Doug Farenick lui répond. 

