Multiple choice

Akash, Manoj and Rama together can complete a piece of work in 10 days. Manoj and Rashid together can complete the work in 15 days. Rama and Rashid together can complete the work in 20 days. If Manoj and Rama together can complete the work in 18 days, find the number of days taken by Akash, Manoj and Rashid to complete the work together.

  1. 6 days

  2. 9 days

  3. 7 days

  4. 5 days

  5. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let A, M, R, Ra be the work rates. A+M+R = 1/10, M+Ra = 1/15, R+Ra = 1/20, M+R = 1/18. We need A+M+Ra. From the equations, (A+M+R) - (M+R) = A = 1/10 - 1/18 = 4/90 = 2/45. Then M+Ra = 1/15. So A+M+Ra = 2/45 + 1/15 = 5/45 = 1/9. The time taken is 9 days.

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