please answer this question
Dear student,
Let the capacity of the cistern be the LCM of 69 and 46 i.e. 138 units.
⇒ The efficiency of Pipe A = 138/69 = 2 units
⇒ The efficiency of Pipe B = 138/46 = 3 units
Since Pipe B is draining, the efficiency of pipe B will be -3.
Now, pipe B starts working first.
⇒ Work done by pipe B and pipe A in 2 hours = -3 + 2 = -1 unit
Now, -1 unit = 2 hours
⇒ -135 units = 135 × 2 = 270 hours
Now, pipe B will be working for the next hour for -3 units and the tank would be empty.
⇒ Total time = 270 + 1 = 271 hours = 11 days 7 hours
Regards!