Question

Two pipes can fill a tank in $25$ and $30$ minutes respectively and a waste pipe can empty 3 gallons per minute. All the three pipes working together can fill the tank in $15$ minutes. The capacity of the tank is:

• A. $120gallons$
• B. $250gallons$
• C. $450gallons$
• D. $500gallons$
• E. $140gallons$

Answer 1

The correct option is C $450gallons$

Water supplied by Pipe 1 be $=\frac{V}{25}$

Water supplied by Pipe 2 be $=\frac{V}{30}$

Water supplied when all pipes are working $=\frac{V}{15}$

So,

$\Rightarrow \frac{V}{25}+\frac{V}{30}-3=\frac{V}{15}$

$\Rightarrow \frac{V}{25}+\frac{V}{30}-\frac{V}{15}=3$

Solving we get

$V=450$ $gallons$

therefore Answer is $\left(C\right)$