Question 292142
ZACHARIAS HAS A TOTAL OF 65 COINS, ALL OF WHICH ARE EITHER DIMES OR NICKELS. THE TOTAL VALUE OF THE COINS IS $5.80. FIND THE NUMBER OF EACH TYPE OF COIN.
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Equations:
Quantity Eq:::: d + n = 65
Value Eq::::::10d+ 5n = 580 cents
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Multiply thru the Quantity Eq. by 10; subtract and solv for "n":
10d + 10n = 650
10d +  5n = 580
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5n = 70
n = 14 (# of nickels)
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Substitute and solve for "d":
d + 14 = 65
d = 51 (# of dimes) 
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Cheers,
Stan H.
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