







Double the number of pennies each week 
20190228 

Donald pose la question : If I save a penny a week,double it every week,How many weeks will it take to reach 1,000,000 dollars Penny Nom lui répond. 





Doubling the area of a pamphlet 
20151031 

Mariam pose la question : A pamphlet has the following dimensions: 4 cm by 6 cm
If the area of the pamphlet is doubled, what will be the length of each side if sides can be integer values only? Penny Nom lui répond. 





Doubling the dimensions of a cone 
20141121 

Hannah pose la question : If the volume of a cone of height 10 cm is 261.8 cm3, show that this
volume is increased by a factor of 8 if the dimensions of the cone are doubled. Penny Nom lui répond. 





Two problems 
20100413 

Dorothy pose la question : 1. Explain why the number 123, 456, 789, 101, 112 cannot be a perfect square. (Hint: What is the units digit?)
2. A substance doubles in volume every minute. At 9:00A.M., a small amount is placed in a container. At 10:00A.M., the container is just full. At what time was the container oneeighth full? Robert Dawson lui répond. 





A cube with twice the volume 
20100411 

Woojin pose la question : From a given cube create another cube with twice the volume.
the cube: 5cm each. Tyler Wood lui répond. 





How much will i have saved in that year? 
20091218 

Loretto pose la question : If i save a penny and it doubles every day for one year how much will i have saved in that year Robert Dawson lui répond. 





A number that ends with 2 
20080623 

Jim pose la question : A number ends in 2. If you were to place that digit at the beginning of the
number, the resulting number will be twice the original. Find the smallest
such number. Stephen La Rocque lui répond. 





Doubling every day 
20071007 

Jerrie pose la question : Patti saved pennies for 10 days. The first day she saved 1 cent. Every day after that she saved twice as much as the day before. How much money did Patti save altogether? Stephen La Rocque lui répond. 





Doubling time 
20050312 

Nick pose la question : Looking for the equation to how many years it will take to double the population given the growth rate is 7%. Penny Nom lui répond. 





33 3/4 doubled 
20040522 

A tailor pose la question : need to know how to add 33 3/4 doubled. How do I come up with the solution? I need to know for measuring garments. Usually I measure on the half meaning on the front of the garment and then double it with the measuring tape but I always get stuck when I need to measure 3/4 such as 66 3/4 doubled and etc. Can you help me figure this out easily. Penny Nom lui répond. 





Doubling the size of an object 
20030401 

Dave pose la question : If I have a known surface area and volume of an unknown object and I want to double the size of the object, how do I find the new area and volume? Walter Whiteley lui répond. 





7x6 by doubling 
20010123 

A student pose la question : Can you think of a way to use doubling to multiply 6x7? Allen Herman lui répond. 





A colony of bacteria 
20000422 

Nicci Demmin pose la question : Suppose that the bacteria in a colony can grow unchecked, by the law of exponential change. The colony starts with one bacterium and doubles every half hour. How many bacteria will the colony contain at the end of 50 hours? Penny Nom lui répond. 

