Question 511594
Coffee A normally costs 75 cents per pound. It is mixed with coffee B, which normally cost 80 cents per pound, to form a mixture that cost 78 cents per pound. If there are 10 pounds of the mix, how many pounds of coffee A were used in the mix?
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Quantity Eq.:::    A    +    B   = 10 lbs.
Value Eq:::::::  75A    +  80B   = 78*10 cents
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Multiply thru the Quantity Eq by 80.
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80A  + 80B = 80*10
75A  + 80B = 78*10
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Subtract and solve for "A":
5A = 2*10
A = 4 lbs (amt. of A needed in the mix)
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Cheers,
Stan H.