Question

Very Good Morring to You students Just a quickquestion.
Jim can fill a pool carrying buckets of water in 30 minutes. Sue can do the same job in 45 minutes. Tony can do the same job in 1 ½ hours. How quickly can all three fill the pool together?

A. 12 minutes
B. 15 minutes
C. 21 minutes
D. 23 minutes
E. 28 minutes

Answer 1

Would you please explain the way that you get the result.

Answer 2

The way to work this out is:
\begin{eqnarray*}
\frac{1}{T} &=& \frac{1}{30}+\frac{1}{45}+\frac{1}{90} \\
\frac{1}{T} &=& \frac{3+2+1}{90} \\
\frac{1}{T} &=& \frac{6}{90} \\
\frac{1}{T} &=& \frac{1}{15} \\
T &=& 15
\end{eqnarray*}
Thereforer the answer is B. 15 minutes.