Question

Two taps 'A' and 'B' can fill a water reservoir in 8 and 6 hours respectively, A third tap 'C' can empty the tank completely in 24 hours.How long would it take to fill the empty tank when all the taps are open?

• A. $4hours$
• B. $5hours$
• C. $6hours$
• D. $3hours$

Answer 1

The correct option is A $4hours$

Tap A can fill in 8 hr. B in 6 hr, C can empty reservoir in 24 hr
All 3 can fill reservoir in 1 hr
$=\frac{1}{8}+\frac{1}{6}-\frac{1}{24}=\frac{6+8-2}{48}=\frac{12}{48}$

All three can fill whole reservoir in $\frac{48}{12}$i.e. 4 hr.