Multiple choice

P and Q together can do a job in 6 days. Q and R together can finish the same job in 60/7 days. P started the work and worked for 3 days. After that Q and R together worked for 6 days and completed the job. Find the difference between number of days taken by R alone and number of days taken by P alone to complete the job?

  1. a)10 days

  2. b)8 days

  3. c)12 days

  4. d)15 days

  5. e)None of these
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A Correct answer
Explanation

P+Q=1/6, Q+R=7/60. P(3) + (Q+R)(6) = 1 => 3P + 6(7/60) = 1 => 3P + 0.7 = 1 => 3P = 0.3 => P = 0.1 (10 days). Q = 1/6 - 1/10 = 1/15. R = 7/60 - 1/15 = 3/60 = 1/20 (20 days). Difference = 20 - 10 = 10 days.

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