Question

Taps A and B can fill a tank in 12 min and 15 min respectively If both are opened and A is closed after 3 min how long will it take for B to fill the tank?

• A. 7 min 45 sec
• B. 7 min 15 sec
• C. 8 min 5 sec
• D. 8 min 15 sec

Answer 1

Answer: (D)

8 min 15 sec

Part fill in 3 minute$=3\times (\frac{1}{12}+\frac{1}{15})$
$\Rightarrow 3\times \frac{9}{60}=\frac{9}{20}$
Remaining part$=1-\frac{9}{20}=\frac{11}{20}$
$\Rightarrow \frac{1}{15}:\frac{11}{20}=1:X$
$\Rightarrow X=\frac{11}{20}\times \frac{15}{1}$
$\Rightarrow X=8.25minute$
So it will take further 8 mins 15 seconds to fill the bucket.