Question

Tap A can fill a cistern in 8 hours and tap B can empty it in 12 hours. How long will it
take to fill the cistern if both of them are opened together?​

Answer 1

Answer:

Tap A can fill 1 tank in 8 hours

Tap A fills in 1 hour =

8

1

tank

Tap B can empty 1 tank in 12 hours.

Tap B empties in 1 hour=

12

1

tank

Both taps will fill in 1 hour =(

8

1

−

12

1

)tank

=

24

3−2

=

24

1

Hence, the tank will be filled completely in 24 hours

Answer 2

☆ Solution ☆

Given :-

• Tap A can fill a cistern in 8 hours and tap B can empty it in 12 hours.

To Find :-

• How long will it take to fill the cistern if both of them are opened together?

Step-by-Step-Explaination :-

A can fill a cistern in 1 hours = $\frac{1}{8}$

B can empty the cistern in 1 hour = $\frac{1}{12}$

Cistern fill in 1 hour when opened together

= $\frac{1}{8} - \frac{1}{12}$

= $\frac{3 - 2}{24} = \frac{1}{24}$

Hence,

Time taken by both of them to fill cistern is 24 hr.