How many gallons of a 15% acid solution must be mixed with a 23% acid solution to get 20 gallons of a 20% acid solution?

Answer 1

X+y = 20

0.15x + 0.23y = 0.2 ( 20) = 4

0.15x + 0.23 ( 20 -x) = 4

0.15x + 4.6 - 0.23x = 4

-0.08x = -0.6

8x = 60

x = 60/8 = 30/4 = 15/2 = 7.5

y = 12.5