Question

. A tap fills a cistern in 4 hours. Another tap empties the full tank
in 6 hours. How long will it take to fill the tank, if the tank is empty
and both the taps are open?

Answer 1

Step-by-step explanation:

Time taken by tap A to fill the cistern =4hours.

Work done by tap A in 1 hour =

1

4

Time taken by tap B to empty the full cistern =6hours.

Work done by tap B in 1 hour =

-1

6

(since, tap B empties the cistern).

Work done by (

A+B

) in 1 hour

4

1

−

16

1

=

12

3−2

=

12

1

part of the tank is filled.

Therefore, the tank will fill the cistern =12hours.