Question

Joan has 40 liters of a 25% solution. How many liters of a 60% solution should she add to make a 30% solution?

Answer 1

C1 x V1 + C2 x V2 = C3 x (V1+V2)

0.25 x 40 + 0.60 x V2 = 0.30 x (40+V2)

10 + 0.60V2 = 12 + 0.30V2

0.30V2 = 2

V2 = 20/3 litres

Answer 2

Let the number of litres of the 60% solution be x

.25(40) + .6x = .3(40+x)

solve for x