What amount of a 60% acid solution must be mixed with a 20% solution to produce 300 mL of a 40% solution?

Question

What amount of a 60% acid solution must be mixed with a 20% solution to produce 300 mL of a 40% solution?

Answer 1

Think "Acid + Acid = Total Acid".

Let x = #mL of 60% solution

y = #mL of 20% solution

x + y = 300 (total mL is 300)

.6x + .2y = .4(300) => .6x + .2y = 120 => 6x + 2y = 1200 (acid + acid = total acid; multiply by 10 to clear decimals).

x + y = 300

6x + 2y = 1200.

Use substitution method or addition/elimination to solve the above system.