Multiple choice

Five pipes fill a tank in 1 hour 20 minutes. If only four pipes of the same type are used, how long will it take to fill the tank?

  1. 1 hour 10 minutes

  2. 1 hour 20 minutes

  3. 1 hour 40 minutes

  4. 1 hour 50 minutes
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Work = 5 pipes * 80 minutes = 400 pipe-minutes. 4 pipes * T = 400. T = 100 minutes = 1 hour 40 minutes.

AI explanation

Using the unitary method, five pipes take 1 hour and 20 minutes, which is 80 minutes. The total work required to fill the tank is equivalent to the work of one pipe operating for 400 minutes (5 pipes multiplied by 80 minutes). If only four identical pipes are used, the time required is the total work divided by 4, which equals 100 minutes. Converting 100 minutes into hours and minutes gives a filling time of 1 hour and 40 minutes.

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