Mixture Problem Mathematics

Question

A scientist needs 20ml of a 18% acid solution for an experiment. The lab has available a 30% solution and a 10% solution. How many ml of the 10% solution should the scientist mix to make the 18% solution?

Answer 1

.3x + .1(20-x) = .18(20)

.2x = .18(20)-.1(20)

x = .08(20)/.2 = 8 ml of 30%

12 ml of 10%

mixed to get 20 ml of 18%

.3(8) + .1(12) = 2.4+1.2 = 3.6 = 20(.18)

30-18=12

18-10 = 8

12/8 = 3/2

3 times as much 10% needed as 30%