Multiple choice

If pipe A can fill a tank in 20 minutes, then 5 pipes, each of 20% efficiency of A, can fill the tank in

  1. 8 min

  2. 100 min

  3. 20 min

  4. 25 min
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Pipe A rate = 1/20. 5 pipes at 20% efficiency = 5 * (0.2 * 1/20) = 5 * (1/100) = 5/100 = 1/20. The combined rate is the same as pipe A, so it takes 20 minutes.

AI explanation

Since each new pipe has 20% of the efficiency of pipe A, each pipe fills the tank at a rate of 20% of 1/20, which equals 1/100 of the tank per minute. With five such pipes operating simultaneously, their combined hourly rate is 5 times 1/100, resulting in 1/20 of the tank per minute. Taking the reciprocal of this combined rate shows that the tank will be filled in 20 minutes.

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