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System of Equations Application Word Problem : Quarters & Dimes

Can I please find out what I am doing incorrectly with the following problem?
"I have seventy five coins in my pocket made up of quarters and dimes. If the total value of the coins is $12.45, how many of each coin do I have?"

q + d = 75 Let q represent quarters
(0.25)q + (0.10)d = 12.45 Let s represent dimes

q = 75 - d

(0.25)(75-d) + (0.10)d = 12.45 q + d = 75
18.75 + 0.25d + 0.10d = 12.45 q + (18) = 75
0.25d + 0.10d = 12.45 - 18.75 q = 75 - 18
0.35d = 6.3 q = 57
d = 18

0.25(57) + 0.10(18) = 12.45
14.25 + 1.8 = 16.05

Solution Preview

q + d = 75 Let q represent quarters
(0.25)q + (0.10)d = 12.45 Let s represent ...

Solution Summary

A system of equations word problem is solved.

$2.19