Question

pipes p and q can fill a tank in 12 minutes and 16 minutes respectively. both are kept open for x minutes, and then q is closed. p fills the rest of the tank in 5 minutes. the value of x is:

Answer 1

Answer:

4 mins

Step-by-step explanation:

Pipe P can fill in 12 mins

⇒ 1 min = 1/12 of the work

Pipe Q can fill in 16 mins

⇒ 1 min = 1/16 of the work

Together, P and Q:

1 min = 1/12 + 1/16 = 7/48

Find the amount of work done P can do in 5 mins:

1 min = 1/12 of the work

5 mins = 1/12 x 5 = 5/12 of the work

Amount of work that was done in x mins:

Amount of work = 1 - 5/12 = 7/12

Find x:

1 min = 7/48 of the work

7/48 of the work = 1 min

1/48 of the work = 1 ÷ 7 = 1/7 min

48/48 of the work  = 1/7 x 48 = 48/7 mins

7/12 of the work = 48/7 x 7/12 = 4 mins

Answer: x = 4 mins