Question

Two pipes A and B can fill a tank in 15 mihutes and 40 minutes respectively. Both the pipes
are opened together but after 4 minutes, pipe A is turned off. What is the total time required to
fill the tank?​

Answer 1

Answer:

29 mins 20 sec

Step-by-step explanation:

Pipe A can fill the tank in 15 mins

Therefore, in 1 min, it can fill 1/15 of the tank

Pipe B can fill the tank in 40 mins

Therefore, in 1 min, it can fill 1/40 of the tank

Find the fraction of the tank filled by both pipes in 4 min

1 min = 1/15 + 1/40 = 11/120

4 mins = 11/120 x 4 = 11/30 of the tank

Find the fraction of the tank to be filled after 4 mins

To be filled = 1 - 11/30 = 19/30 of the tank

Find the amount of time Pipe B needs to fill up the rest of the tank:

1 min = 1/40

Number of minutes needed = 19/30 ÷ 1/40 = 76/3 mins = 25 mins 20 sec

Find the total time needed to fill the tank:

Total time = 4 mins + 25 mins 20 sec = 29 mins 20 sec

Answer: It takes 29 mins and 20 sec to fill the tank.