Your piggy bank contains $19.75 in dimes and quarters. There are 100 coins in all. How many dimes are there?

Your piggy bank contains $19.75 in dimes and quarters. There are 100 coins in all. How many dimes are there?

Detailed Explanation

Let x equal the number of dimes. Then 100 – x represents the number of quarters. There is 0.10x in dimes and 0.25(100 – x) in quarters.

0.10x + 0.25(100 – x) = 19.75

0.10x + 25 – 0.25x = 19.75

–0.15x = –5.25

x = –5.25/–0.15

x = 35

0.10x + 0.25(100 – x) = 19.75

0.10x + 25 – 0.25x = 19.75

–0.15x = –5.25

x = –5.25/–0.15

x = 35