1.

A cistern can be filled by two pipes in 10 and 12 min respectively. Both the pipes are opened together for a certain time but, due to defects, only 1/6th of full quantity of water flows through the former and 2/5th of the latter. The defects are detected and rectified. The cistern is filled in 3 min from that moment. How long was it before the detects were rectified?1). 8 min2). 8.5 min3). 9 min4). 10 min

Answer»

Pipe A can fill the tank in 10 MIN.

Pipe B can fill the tank in 12 min.

Total units to be filled in the cistern = LCM of (10, 12) = 60

⇒ Pipe A can fill 6 units of WATER in 1 min.

⇒ Defected Pipe A can fill (6 × 1/6) = 1 UNIT of water in 1 min.

⇒ Pipe B can fill 5 units of water in 1 min.

⇒ Defected Pipe B can fill (5 × 2/5) = 2 units of water in 1 min.

Given that, last 3 min, both the pipes used were rectified

⇒ in last 3 min (6 + 5) × 3 = 33 units of water were filled in the tank.

⇒ (60 - 33) = 27 units of water were filled with defected pipes.

Both Defected pipes can fill 3 units of water in 1 min.

⇒ Defected pipes can fill 27 units of water in (27/3) = 9 min.

∴ After 9 minutes the defects were rectified.


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