Question

Use a system of equations to solve this problem.

A chemist currently has two solutions of sodium chloride. One solution has a 5% concentration and the other has a 25% concentration. The chemist needs to make 10 L of a 10% sodium chloride solution.

Let x = the amount of 5% solution.

Let y = the amount of 25% solution.



How much of each solution does the chemist need to make?

Enter your answers, as decimals, in the boxes.

____ L of 5% solution


____ L of 25 % solution

Answer 1

We have to set up 2 equations:
A) x + y = 10 liters
B) .05x + .25y = 10 * .10

Multiply equation B) by -4
B) -.2x  - y = -4 then add to equation A)
A) x + y = 10 liters
.8x = 6 liters
x = 7.5 liters of 5%
y = 2.5 liters of 25%