M7MBA wrote: ↑

Thu Oct 01, 2020 6:50 am

A drum of bathroom cleaner contains \(200\) gallons of a cleaning solution that is \(20\%\) bleach. If \(50\) gallons of water are added to the solution, what percent of the new solution is composed of bleach?

A. \(12\%\)
B. \(15\%\)
C. \(16\%\)
D. \(18\%\)
E. \(20\%\)

Answer: C

Solution:

The cleaner contains 200 x 0.2 = 40 gallons bleach and thus 160 gallons water. If 50 gallons of water are added to the solution, the new solution will be composed of 40/250 = 4/25 = 16/100 = 16% bleach.

Alternate Solution:

We have 200 gallons of 20% bleach, and we add 50 gallons of water containing 0% bleach. We now have 250 gallons of a solution with an unknown bleach concentration. Let’s put this information into an equation:

200(0.20) + 50(0) = 250(x)

40 + 0 = 250x

40/250 = x

0.16 = x

Thus, the new solution is 16% bleach.

Answer: C