Multiple choice

Pipe A, B and C fill a tank alone in 10,15 and 20 min respectively. All the pipe open for 3 min than pipe C is closed than find in how many min pipe A and B can fill the rest of the part?

  1. 12.3

  2. 22.5

  3. 2.1

  4. 3.3

  5. 3.36
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Rates: A=1/10, B=1/15, C=1/20. Combined rate = 6/60 + 4/60 + 3/60 = 13/60. In 3 mins, they fill 3 * 13/60 = 39/60 = 13/20. Remaining part = 7/20. Rate of A+B = 1/10 + 1/15 = 3/30 + 2/30 = 5/30 = 1/6. Time = (7/20) / (1/6) = 42/20 = 2.1 minutes.

AI explanation

Using the least common multiple method for 10, 15, and 20 minutes, let the total capacity be 60 units. Pipes A, B, and C fill at rates of 6, 4, and 3 units per minute, respectively, making their combined rate 13 units per minute. In the first 3 minutes, they fill 39 units, leaving 21 units to be filled. With pipe C closed, the combined rate of pipes A and B is 6 + 4 = 10 units per minute. Dividing the remaining 21 units by 10 gives 2.1 minutes to fill the rest of the tank.

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