Question 1095715: a parking meter contains quarters and dimes worth $11.55. There are 66 coins in all find out how many of each there are Answer by ikleyn(52775) (Show Source):
Let "D" be the number of dimes.
Then the number of quarters is (66-D).
The dimes contribute 10*D cents to the total.
The quarters contribute 25*(66-D).
The total is 1155 cents, and the "value equation" is
10*D + 25*(66-D) = 1155.
Simplify and solve for D:
10*D + 25*66 - 25D = 1155,
10D + 1650 - 25D = 1155,
-15D = 1155 - 1650,
-15D = 495,
D = = 33.
Answer. 33 dimes and 66-33 = 33 quarters.
Check. 33*10 + 33*25 = 1155 cents = $11.55.
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