Question 170521
A child's bank contains $6.30 in dimes and quarters. There are twice as many dimes as quarters. How many of each kind of coin are there in the bank?
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d = 2q
10d + 25q = 630
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Rearrange:
 d  -  2q = 0
10d + 25q = 630
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Use substitution to solve for "q":
10(2q) + 25q = 630
45q = 630
q = 14 (# of quarters)
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d = 2q = 28 (# of dimes)
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Cheers,
Stan H.