Question

a water tank is two-fifth full. pipe a can fill a tank in 10 minutes, and pipe b can empty it in 6 minutes. if both the pipes are opened, how long will it take to empty or fill the tank completely?

Answer 1

In one minute :

Amount filled = 1/10

Amount emptied = 1/6

Total amount retained in 1 minute :

1/10 - 1/6 = - 1/15

This means every 1 minute :

1/15 is removed.

If the tank is 2/5 full, how long will it take to empty it.

In 1 minute 1/15 is emptied

How about 2/5 :

2/5 × 15/1 × 1 = 6

= 6 minutes

Answer 2

Step-by-step explanation:

A can filled the tank in => 10 minutes

:- A can filled the tank in 1 minutes => 1/10 min

B can empty the tank in => 6 minutes

:- B can empty the tank in 1 minutes => 1/6 min

:- If both are opened to empty the tank

=> 1/6 - 1/10

=> 5 - 3/30

=> 2/30

=> 1/15

:- Total time taken

=> 1 ÷ 1/15

=> 15

:- A water tank is full => 2/5

:- It will empty in

=> 2/5 × 15

=> 2 × 3

=> 6 (ans)

:- It will empty in 6 min if the both tap are opened