Question

A pharmacist needs to strengthen a 15% alchohol solution to one of 32% alchohol. How much pure alchohol should be added to 800ml of 15% solution?

Answer 1

Let x = the required number of milliliters of pure alcohol.
Then we have:
800(15%) + x(100%) = (800+x)(32%) Change the percents to decimals.
800(0.15) + x(1) = (800+x)(0.32) Simplify and solve for x.
120 + x = 256 + 0.32x Subtract 0.32x from both sides.
120 + 0.68x = 256 Subtract 60 from both sides.
0.68x = 136 Divide both sides by 0.68
x = 200 ml of pure alcohol is required.