If a change dispenser contains 32 coins consisting of only dimes and quarters worth $5.15, how many
dimes are in the dispenser?

Work Shown:

d = number of dimes

q = 32-d = number of quarters

$5.15 = 515 cents

10d+25q = 515

10d+25(32-d) = 515

10d+800-25d = 515

-15d+800 = 515

-15d = 515-800

-15d = -285

d = -285/(-15)

d = 19

There are 19 dimes. You can stop here if you want.

q = 32-d = 32-19 = 13

There are 13 quarters

Check:

1 dime = 10 cents

19 dimes = 19*10 = 190 cents

1 quarter = 25 cents

13 quarters = 13*25 = 325 cents

total value = 190 cents + 325 cents = 515 cents = $5.15

The answer is confirmed.