How Much Time will be Taken by B to Fill the Tank? If

Pipe A alone can fill a tank in 8 hours. Pipe B alone can fill the same tank in 6 hours. If both the pipes are opened but after 2 hours pipe A is closed, then pipe B will fill the tank in

  1. 6 hours
  2. 7/2 hours
  3. 4 hours
  4. 5/2 hours
Monis Rasool Professor Asked on 10th June 2015 in Maths.
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1 Answer(s)

Answer: (4) 5/2 hours.
Explanation:-
Pipe A alone can fill a tank = 8 hours
therefore, Pipe A alone can fill a tank in 1 hour = 1/8

Pipe B alone can  fill a tank = 6 hours
Therefore, Pipe B alone can fill a tank in a hour = 1/6

Both pipe can fill the tank = 2(1/8 + 1/6)
= 1/ 4 + 1 /3
= 7/12
Part of empty tank = 1 – 7/12
= (12 – 7)/12 = 5/12
B can fill the tank = 5 x 6 /12 = 5/2 hours.
Hence, the answer is (4) 5/2 hours.

Anurag Mishra Professor Answered on 14th June 2015.
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