Question 391237
A collection of nickels and dimes is worth $3.30. There are 42 coins in all. How many of each kind of coin are there? 
this is the equation i wrote: 
.05x + .10y = 3.30
x + y = 42
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Multiply thru 1st Eq. by 100.
Multiply thru 2nd Eq. by 5.
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5x + 10y = 330 cents
5x + 5y  = 5*42
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Subtract and solve for "y":
5y = 120
y = 24 (# of dimes)
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Since x+y = 42, x = 42-24 = 18 (# of nickels)
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Cheers,
stan H.