Question

6. two pipes a and b can fill a tank in 4 hr and 5 hr respectively. If they are turned on alternately for one her. Each, the tank is filled in (assume it is a that starts)

Answer 1

A 1 hr work = 1➗4

B 1 hr work = 1➗5

A is opened in first hour

Part of tank filled in 1st hr = 1➗4

B is opened at the 2nd hr

Part of tank filled in 2nd hr = 1➗4➕1➗5 = 9➗20

In 2 hrs ---> 9➗20 part filled

In 4 hrs --> x part filled

x = 4➗2 ✖9➗20

x = 18➗20

So in 4 hrs part of tank filled = 19➗10

Remaining to be filled = 1 ➖ 9➗10 = 1➗10

So in 5th hr, A2be kept opened

A 2 fill 1➗4 part --> In 1 hr

A2 fill 1➗10 part -->In x hr 

x = 4➗10 = 2➗5hrs = 2➗5✖ 60 mins = 24mins

So total time taken = 4 hrs + 24 mins

thank you ☺