Two pipes A and B can fill a tank in 6 hours and 9 hours respectively They are opened alternately fo...........

Quantitative Aptitude (CPO) Pipes&cistern

Two pipes A and B can fill a tank in 6 hours and 9 hours respectively. They are opened alternately for 1 hour each, starting with pipe A

first. In how many hours will the tank be filled ?

This questions was previously asked in

SSC CPO 12th-March-2019-Shift-1

- Pipe A fills the tank in 6 hours, so it fills 1/6 of the tank in an hour.

- Pipe B fills the tank in 9 hours, so it fills 1/9 of the tank in an hour.

- Open pipe A for the first hour: 1/6 of the tank is filled.

- Open pipe B for the next hour: 1/9 of the tank is filled.

- Total filled in 2 hours is 1/6 + 1/9 = 5/18 of the tank.

- Repeat this cycle (2 hours) until the tank is almost full.

- After 6 hours, the tank is filled (5/18 * 3 = 15/18 = 5/6 full).

- Open pipe A for one more hour, adding 1/6, making it filled to:

5/6 + 1/6 = 1 full tank.

- Thus, the tank will be filled in 7 hours.

Correct Answer: Option 4: 7

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