SOLUTION: We would like to create 20 gallons of solution that is 25% acid. How many gallons each, of a 10% acid solution and a 30% acid solution would we mix?

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Question 1112659: We would like to create 20 gallons of solution that is 25% acid. How many gallons each, of a
10% acid solution and a 30% acid solution would we mix?

Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
25% target is three-quarters of the way from 10% to 30%.
25% is closer to 30% than it is to 10%, so need more of the 30% than the 10%.

%283%2F4%29%2A20=15, gallons of the 30% acid

%281%2F4%29%2820%29=5, gallons of the 10% acid.


Does that pair of results work?
5%2A0.10%2B15%2A0.30=20%2A0.25
0.5%2B4.5=5
5.0=5------true

The answer found works.
5 gallons of the 10%
and 15 gallons of the 30%

Answer by ikleyn(52786) About Me  (Show Source):
You can put this solution on YOUR website!
.
You can solve the problem algebraically and/or intuitively.

Intuitive solution is this:

    On each gallon of the 10% solution take 3 gallons of the 30% solution.


    It works, since  %280.1%2A1+%2B+0.3%2A3%29%2F%283+%2B+1%29 = 1.0%2F4 = 0.25 = 25%.


    Thus you get 5 groups/packages each containing (1 gallon of the 10% solution PLUS 3 gallons of the 30% solutions),

    which gives you 5 gallons of the 10% solution AND 15 gallons of the 30% solutions, in all.


Algebraic solution is this:

    %280.1%2Ax+%2B+0.3%2A%2820-x%29%29%2F20 = 0.25.


    saying that the concentration of the mixture is 25% = 0.25.


    The steps to solve it are

        0.1x +0.3*(20-x) = 0.25*20

        0.1x + 6 - 0.3x = 5

        -0.2x = 4 - 5 = -1  ====>  x = %28-1%29%2F%28-0.2%29 = 5.


    You get the same answer:  5 gallons of the 10% solution and (20-5) = 15 gallons of the 30% solution.

Solved.