Question

Using a hose, it takes $9$ hours to fill a swimming pool. Using an irrigation pump, it takes $3$ hours.
If you use both the hose and pump together, how long will it take to fill the pool?

• A. $2hours$
• B. $2hours15minutes$
• C. $2hours45minutes$
• D. $3hours$
• E. $6hours$

Answer 1

The correct option is B $2hours15minutes$

Work efficiency of hose in filling pool = $\frac{1}{9}$ per hour

Work efficiency of irrigation pump in filling pool= $\frac{1}{3}$ per hour

$\therefore$ work done by both together = $\frac{1}{9}+\frac{1}{3}=\frac{4}{9}$per hour

Hence time taken to fill the tank $100$% = $\frac{9}{4}$ hours = $2.25$ hours

Since, $1hour=60minutes$

$\therefore 2.25$ hours = $2.25\times 60=135$ minutes

now, $135$ minutes = $(60+60+15)$ minutes = $2hours$ $15minutes$

So, the answer is option B