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1. A water tank can be filled by two pipes A and B in 60 minutes and 40 minutes respectively. How many minutes will it take to fill the tankfrom empty state if B is used for half the time , and A B fill it together for the other half?

  • A. 30 min
  • B. 30 min
  • C. 30 min
  • D. 30 min

Answer: Option A

Explanation:

Part filled by (A + B) in 1 minute = (1/60 + 1/40) = 1/24

Suppose , the tank is filled in x minutes

Then x/2 ( 1/24 + 1/40) = 1

x/2 × 1/15 = 1

x = 30 min

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