Question

scientist needs 120 liters of a 20% acid solution for an experiment. The lab has available a 25% and a 10% solution. How many liters of the 25% and how many liters of the 10% solutions should the scientist mix to make the 20% solution?

Answer 1

The scientist needs 80 liters of 25% solution and 40 liters of 10% solution.

Explanation:

If x is the liters of 25% solution, and y is the liters of 10% solution, then:

x + y = 120

0.25x + 0.10y = 0.20(120)

Solve the system of equations using substitution or elimination. Using substitution:

0.25x + 0.10(120 − x) = 0.20(120)

0.25x + 12 − 0.10x = 24

0.15x = 12

x = 80

y = 40

The scientist needs 80 liters of 25% solution and 40 liters of 10% solution.