Question 1006550
 a piggy bank contains 91 coins which are nickles, dimes and quarters. there are twice as many quarters as dimes, and half as many nickles as dimes. how much is in the piggy bank? 
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Equtions:
n + d + q = 91 coins
q = 2d
n = d/2
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Substitute for "q" and "n" and solve of d::
2d + d + d/2 = 91
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(7/2)d = 91
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(1/2)d = 13
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dimes = 26 (# of dimes)
q = 2d = 52 (# of quarters)
n = d/2 = 13 (# of nickels)
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Cheers                                                                        s,
Stan