Question 256611
Here is a word problem i am having trouble with. 
A coin collection contains nickels, dimes, and quarters. 
there are twice as many dimes as quarters
d = 2q
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and seven more nickels than dimes.
n = d + 7
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the total value of all the coins is $2.00.
5n + 10d + 25q = 200 cents
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How many quarters are in the collection?
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Rearrange:
q = (1/2)d
n = d+7
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Substitute into the value equation and solve for "d":
5(d+7) + 10d + 25(1/2)d = 200
5d + 35 + 10d + 12.5d = 200
27.5d = 165
d = 6 (# of nickels)
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Since q = (1/2)d, q = (1/2)6 = 3 (# of quarters)
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Cheers,
Stan H.