A box of 80 coins, consisting of only nickels and dimes, is worth 7 dollars and 80 cents. Find the number of nickels.

1 answer:

8 0

4 nickles
Explanation:
80=N+D
7.80=0.05N + 0.1D

D=80-N

7.80=0.05N + 0.1(80-N)
7.80=0.05N + 8 - 0.1N
0.1N + 7.80 = 8 + 0.05N
0.05N = 8-7.80
0.05N = 0.2
N= 4

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