Multiple choice

Pipe - I and pipe - II can fill a tank in 12 hours. Pipe - II and pipe - III can fill the same tank in 15 hours. If capacity of pipe - I is double of that of pipe - III, then in how many hours pipe - I alone could fill the tank?

  1. 60

  2. 30

  3. 20

  4. 15
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let I, II, III be rates. I+II = 1/12, II+III = 1/15, and I = 2*III. Substituting: 2*III + II = 1/12 and II + III = 1/15. Solving gives III = 1/60, so I = 2/60 = 1/30, meaning 30 hours.

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