A collection of nickels and dime has a total value of $8.50. How many coins are there if there are 3

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A collection of nickels and dime has a total value of $8.50. How many coins are there if there are 3 times as many nickels as dimes.

Let n be the number of nickels. Let d be the number of dimes. We're give two equations:

1. n = 3d
2. 0.1d + 0.05n = 8.50

Plug equation (1) into equation (2) for n:
0.1d + 0.05(3d) = 8.50

Multiply through:
0.1d + 0.15d = 8.50

Type this equation into our search engine and we get:
d = 34

Now, we take d = 34, and plug it back into equation (1) to solve for n:
n = 3(34)
n = 102