Question

A chemist is using 389 milliliters of a solution of acid and water. If 18.6% of the solution is acid, how many milliliters of acid are there?

Answer 1

Explanation:

for questions about % always find out first what 100% or what 1% are.

everything else can be calculated out of these 2 numbers.

in our case here

100% = 389 ml

1% = 100%/100 = 389/100 = 3.89 ml

18.6% = 18.6×1% = 18.6 × 3.89 = 72.354 ml

so, there are 72.354 ml of acid in the solution.

FYI

as you can see, we can combine both steps into one and do any of the following

18.6% = 18.6 × 100%/100 = 18.6 × 389/100 =

= (18.6/100) × 389 = 0.186 × 389