







Double the number of pennies each week 
20190228 

From Donald: If I save a penny a week,double it every week,How many weeks will it take to reach 1,000,000 dollars Answered by Penny Nom. 





Doubling the area of a pamphlet 
20151031 

From Mariam: 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? Answered by Penny Nom. 





Doubling the dimensions of a cone 
20141121 

From Hannah: 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. Answered by Penny Nom. 





Two problems 
20100413 

From Dorothy: 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? Answered by Robert Dawson. 





A cube with twice the volume 
20100411 

From Woojin: From a given cube create another cube with twice the volume.
the cube: 5cm each. Answered by Tyler Wood. 





How much will i have saved in that year? 
20091218 

From Loretto: If i save a penny and it doubles every day for one year how much will i have saved in that year Answered by Robert Dawson. 





A number that ends with 2 
20080623 

From Jim: 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. Answered by Stephen La Rocque. 





Doubling every day 
20071007 

From Jerrie: 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? Answered by Stephen La Rocque. 





Doubling time 
20050312 

From Nick: Looking for the equation to how many years it will take to double the population given the growth rate is 7%. Answered by Penny Nom. 





33 3/4 doubled 
20040522 

From A tailor: 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. Answered by Penny Nom. 





Doubling the size of an object 
20030401 

From Dave: 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? Answered by Walter Whiteley. 





7x6 by doubling 
20010123 

From A student: Can you think of a way to use doubling to multiply 6x7? Answered by Allen Herman. 





A colony of bacteria 
20000422 

From Nicci Demmin: 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? Answered by Penny Nom. 

