davidd (davidd) wrote,


From pastilla: How many oz of 40% alcohol must be mixed with 10 oz of 70% alcohol to give a solution that is 45% alcohol? (fun GRE question)

After initially stumbling over the same basic subtraction as dblume (like, 7 - 4.5 = two point five, duh....) I solved the problem this way:

.4x + .7(10) = .45(10+x)
.4x + 7 = .45(10+x)
.4x + 7 = 4.5 + .45x
.4x = -2.5 + .45x
.05x = 2.5
x = 50 oz

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