Question

A scientist wants to create 120 ml of a solution that is 30% acidic. To create this solution, she has access to a 20% solution and a 45% solution. How many millimeters of each solution should she combine to create the 30% solution? Solve this problem using a system of two equations in two variables.

Answer 1

The solution for this problem is: 

First, you need to multiply the solution to the 30 percent
120 x .3 = 36

m + n = 125

2m + 45n = 36
2m + 2n = 240

3n = 120

n = 40

m = 80

Therefore, you need 80 ml of 20% solution and 40 ml of 45% solution to make 120 ml solution of 30% solution.