Multiple choice

It was observed that a red pipe takes 20 minutes to fill a bucket while a blue pipe took 30 minutes to fill the same bucket. How much time would it take to fill the bucket if both the pipes were used simultaneously?

  1. 10 minutes

  2. 11 minutes

  3. 12 minutes

  4. 13 minutes
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The red pipe fills 1/20 of the bucket per minute, and the blue pipe fills 1/30 of the bucket per minute. Together, they fill (1/20 + 1/30) = (3/60 + 2/60) = 5/60 = 1/12 of the bucket per minute. Thus, it takes 12 minutes to fill the bucket.

AI explanation

Using the least common multiple method, let the capacity of the bucket be 60 units. The red pipe fills the bucket at a rate of 60 / 20 = 3 units per minute, while the blue pipe fills it at a rate of 60 / 30 = 2 units per minute. When operating simultaneously, their combined filling rate is 3 + 2 = 5 units per minute. Dividing the total capacity of 60 units by this combined rate of 5 units per minute shows that the bucket will be filled in 12 minutes.

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