Multiple choice

Which information are necessary to answer the questions asked- Pipe D is opened for first 6 minutes then closed and pipe C is opened. Find the time taken by pipe C to fill the remaining part of the tank. (I). Pipe A and pipe B together can fill a tank in 15 minutes. (II). Pipe A, Pipe B and Pipe D they can fill the tank in 12 minutes. (III). Pipe C and pipe D together can fill the tank in 10 minutes.

  1. All I, II and III

  2. Only II and III

  3. Only II

  4. Any two of the three

  5. Even I, II and III together are not sufficient
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

To find the time for pipe C alone, we need its rate. Pipe D's rate can be found from (I) and (II) together: (A+B) = 1/15 and (A+B+D) = 1/12 gives D = 1/12 - 1/15 = 1/60. Statement (III) gives (C+D) = 1/10, so C = 1/10 - 1/60 = 1/12, meaning C takes 12 minutes. All three statements are required.

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