Question

Lisa's penny bank is 1/10 full. After she adds 440 pennies, it is 3/5 full. How many pennies can Lisa's bank hold?

Answer 1

Explanation:

After the 440 pennies are added, the bank is 3/5 full. It started out 1/10 full, so

3/5 - 1/10 is the amount of space in the bank that the 440 pennies took up, or

1/2. Use proportions to solve this, with number of pennies on the top and the fraction of the bank that is filled on the bottom:

`(440)/((1)/(2) )=(x)/(1)`

where x is the number of pennies (our unknown) that it will take to fill the bank (1). Cross multiply to get

`(1)/(2)x=440`

so x = 880