SOLUTION: How many gallons of 15% alcohol solution and 45% alcohol solution must be mixed to get 9 gallons of 25% alcohol solution?

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Question 919461: How many gallons of 15% alcohol solution and 45% alcohol solution must be mixed to get 9 gallons of 25% alcohol solution?
Found 2 solutions by ewatrrr, richwmiller:
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
x 45% amount
.45x + .15(9G-x) = .25(9G)
x = .10(9G)/.3, 45% amount. 9-x the 15% amount

Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
We need a total of 9 gal at 25%
We want to know how many gal at 15% to mix with 45%
a+b=9,
0.15*a+0.45*b=0.25*9
a=9-b
0.15*(9-b)+0.45*b=2.25
1.35-0.15b+0.45*b=2.25
0.3*b=0.9
b=3
a=9-b
a=6 gal at 15%
b=3 gal at 45%
check
0.15*6+0.45*3=0.25*9
0.9+1.35=2.25
2.25=2.25
ok
codemx1