<PRE><B>Question 260831</B>
what quantity x of a 75% acid solution must be mixed with a 25% solution to produce 500ml of a 40% solution?
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Quantity Equation:::::    x +     y = 500 ml
active ingredient Eq.:0.75x + 0.25y = 0.40*500 ml
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Multiply thru 1st Equation by 25
Multiply thru the 2nd Eq. by 100
25x   +  25y  = 25*500
75x   +  25y  = 40*500
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Subtract the 1st from the 2nd Eq.
50x = 15*500
x = 15*10
x = 150 ml (amount of 75% solution needed in the mixture)
Since x + y = 500, y = 350 ml (amount of 25% solution needed in the mixture)
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Cheers,
Stan H.
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