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?

First lets change the fractions so they have common denominators:

3/5 = 6/10

The bank was 1/10, after adding the pennies it was 6/10

6/10 - 1/10 = 5/10 = 1/2

This means 400 pennies filled 1/2 the piggy bank.

There are 2 halves (1/2) to a whole (full piggy bank).

The piggy bank can hold 400 x 2 = 800 pennies.