How many liters of a 4 \% solution of salt should be added to a 28 \% solution in order to obtain 1440 liters of a 20 \% solution?

Question

How many liters of a 4 % solution of salt should be added to a 28 % solution in order to obtain 1440 liters of a 20 % solution?

Answer 1

Let x = number of liters of 4% solution

 

1440 - x = number of liters of 28% solution

 

0.04x + 0.28(1440 - x) = 0.20(1440)

 

0.04x + 403.2 - 0.28x = 288

 

                    -0.24x = -115.2

 

                           x = 480 liters

 

Mix 480 liters of 4% salt solution with 960 liters of 28% salt solution to obtain 1440 liters of 20% salt solution.