Question

In Frank's piggy bank, there are only quarters

and dimes. He has 37 coins, and has a total of
$5.50. How many quarters does he have?

Answer 1

12 quarters

Explanation:

number of quarters ---------x

number of dimes ------------y

therefore, x + y = 37---------------times 10 both sides --------10x + 10y = 370-------equation 1

0.25x + 0.1y = 5.5 -----times 100 both sides -------25x + 10y = 550 ------equation 2

equation 2 minus equation 1 is 25x + 10y - 10x - 10y = 550 - 370 ------ 15x = 180 -------x = 12

there are 12 quarters