Question 183322
Christina makes a $9.25 purchase at a bookstore with a $20 bill. The store has no bills and gives her change in quarters and fifty cent pieces. There are 30 coins in all. How many of each kind are there?
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Amount of change = 20.00-9.25 = 10.75
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Equations:
Quantity Equation: q  + f  = 30
Value  Equation..:25q +50f = 1075 cents
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Multiply thru the 1st be 25:
25q  +  25f =  25*30
25q  +  50f = 1075
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Subtract 1st from 2nd to solve for "f"
25f = 1075-25*30
f = 13 (# of fifty cent pieces)
Since q + f = 30, q = 27 (# of quarters)
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Cheers,
Stan H.