Multiple choice

A certain job can be completed by Prem and Suresh together in 24 days, by Suresh and Vikram together in 30 days, and by Vikram and Prem together in 40 days. In how many days can Prem alone finish the same job?

  1. 50 days

  2. 60 days

  3. 65 days

  4. 70 days

  5. 75 days
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let P, S, V be the work rates. P+S=1/24, S+V=1/30, V+P=1/40. Summing these gives 2(P+S+V) = 1/24 + 1/30 + 1/40 = (5+4+3)/120 = 12/120 = 1/10. Thus P+S+V = 1/20. P = (P+S+V) - (S+V) = 1/20 - 1/30 = 1/60. Prem takes 60 days.

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