Multiple choice

There are two inlet pipes (A,

  1. 8 hr

  2. 6 hr

  3. 10 hr

  4. 12 hr

  5. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
AI explanation

Inlet pipes A and B have rates of 1/15 and 1/10, so their combined rate is 1/15 + 1/10 = 1/6 of the tank per hour. When opened for 4 hours, they fill 4 times 1/6, which is 2/3 of the tank. Outlet pipes C and D have emptying rates of 1/20 and 1/30, giving a combined emptying rate of 1/20 + 1/30 = 1/12 of the tank per hour. Emptying 2/3 of the tank at this rate takes (2/3) divided by (1/12), equalling 8 hours.

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