Seven gallons of 4% acid is mixed with some 1% acid to produce a 2% acid solution. How much 1% acid is required, and how many gallons of 2% solution would this make?

Question

Seven gallons of 4% acid is mixed with some 1% acid to produce a 2% acid solution. How much 1%

acid is required, and how many gallons of 2% solution would this make?

Answer 1

7(.04) + x(.01) = (7+x)(.02)

.28 + .01x = .14 + .02x

.01x = .14

x = 14 gallons of 1% mixed with 7 gallons of 4% yield 21 gallons of 2%

4 is within 2 of 2

1 is within 1 of 1

2/1 = 14/7

twice as much of the closer percentage is needed