Multiple choice

Two pipes can fill a tank in 10 minutes together if the efficiency of the first pipe is 8 times the efficiency of the second pipe find the time required to fill the tank using the second pipe alone.

  1. 88 minutes

  2. 87 minutes

  3. 89 minutes

  4. 90 minutes

  5. 93 minutes
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let efficiency of second pipe be x, then first is 8x. Combined efficiency = 9x. Time = 10 mins. Total work = 90x. Time for second pipe = 90x / x = 90 minutes.

AI explanation

Using the constant work equivalence method, if the first pipe is 8 times as efficient as the second, it works 8 times faster and would take 1/8 the time. Let the time taken by the second pipe be T, meaning the first pipe takes T/8 minutes. Their combined rate is 1/T + 8/T = 9/T, which equals 1/10 of the tank per minute, yielding the equation 9/T = 1/10. Solving this gives T = 90 minutes.

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