How many quarters? How many dimes?

Question

A parking meter contains quarters and dimes worth ​$8.40. There are 48 coins in all. Find how many of each there are.

Answer 1

Let x = the number of dimes

Let y = the number of quarters

x + y = 48

y = 48 - x

.10x + .25y = 8.40

Multiply both sides by 100. It just makes it easier to get rid of the decimal points.

10x + 25y = 840

10x + 25(48 - x) = 840

10x + 1200 - 25x = 840

-15x = -360

x = 24 dimes

y = 48 - 24 = 24 quarters