Question

A chemist has a 20% and a 40% acid solutions. What amount of each solution should be used in order to make 300 ml of a 28% acid solution?

Answer 1

Let x be the solution at 20% and y be the solution at 40%, hence

x + y = 300 ml

We now write an equation that expresses that the total acid in the final 300 ml is equal to the sum of the amounts of acid in x and y

28% * 300 = 20% * x + 40% * y

Solve the above system of equations to find

x = 180 and y = 120

180ml and 120 ml