SOLUTION: A box contains 66 coins, only dimes and nickels. The amount of money in the box is $5.15. How many dimes and how many nickels are in each box?

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Question 955131: A box contains 66 coins, only dimes and nickels. The amount of money in the box is $5.15. How many dimes and how many nickels are in each box?
Answer by addingup(3677) About Me  (Show Source):
You can put this solution on YOUR website!
Let's call dimes d and nickels n:
d+n = 66 (equation 1)
0.10d+0.05 n = 5.15 (equation 2)
Multiply all the terms in equation 1 times 0.10
0.10d+0.10n= 6.6
Subtract equation 1 from equation 2:
0.10d+0.05n=5.15
-0.10d+0.10n=6.6
------------------
0d - 0.05n = -1.45
We have no more d’s, so we can rewrite:

-0.05n= -1.45 Multiply both sides times -1
0.05n = 1.45 Divide both sides by 0.05:
n = 29 We have 29 nickels, and since:
d= 66-n
d= 66-29= 37
Proof:
29(0.05)= 1.45
37(0.1)= 3.70
1.45+3.70 = 5.15 We have the correct answer