Question

A pharmacist wishes to mix a solution that is 4% Minoxidil. She has on hand 90 ml of a 1% solution and wishes to add some 6% solution to obtain the desired 4% solution. How much 6% solution should she add?

Answer 1

Explanation:

remember, 1% = 1/100 = 0.01

4% = 0.04

6% = 0.06

so, we have to find the solution for

90×0.01 + x×0.06 = (90+x)×0.04

with x being the amount needed of the 6% solution.

90×0.01 + x×0.06 = 90×0.04 + x×0.04

90×0.01 + x×0.02 = 90×0.04

x×0.02 = 90×0.03

x = 90×0.03/0.02 = 135 ml

so, we need to add 135 ml of the 6% solution to get in total a 4% solution (90+135 = 225 ml of that).