a scientist needs 10 litres of a 20% acid solution for an experiment, but she has only a 5% solution and a 40% solution. to the nearest tenth of a liter, about how many litres of the 5% and the 40% should she mix to get the solution she needs?
10 liters total
x = 5% amount of acid = .05x
10-x = 40% amount of acid = .40 (10-x)
Sum of ingredients = amount in final solution
.05x + .40(10-x) = .20 ( 10)
solve for x the 5% amount then 40% amount = 10-x liters