Steve has a bag of money amounting to $4.32. It contains 108 coins, all of them dimes or pennies. How many pennies are there?
If we let d represent the number of dimes and p the number of pennies, we have two equations:
d + p = 108
10d + p = 432
Substituting p = 108 – d in the second equation, we get:
10d + (108 – d) = 432
or 9d = 324, so d = 36 and p = 72
Check: 36($.10) + $.72 = $4.32.