Ravi and Sanju together can do a job in 2 days, Sanju and Mahesh can do it in 4 days, while Ravi and Mahesh can do it in 2 days. What is the number of days required for Ravi to do the same job alone?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is Option 2 i.e. .
Ravi(R) and Sanju(S) together can do a job in 2 days.
Sanju(S) and Mahesh(M) can do a job in 4 days.
Ravi(R) and Mahesh(M) can do a job in 2days.
⇒ Work done in 1 day by (R + S) = 1/2 ..(1
⇒ Work done in 1 day by (S + M) = 1/4 ..(2
⇒ Work done in 1 day by (R + M) = 1/2 ..(3
Adding eq(1, (2, and (3, we get -
⇒ Work done in 1 day by 2(R + S + M) = 1/2 + 1/4 + 1/2 = (2 + 1 + 2)/4 = 5/4
⇒ Work done in 1 day by (R + S + M) = 5/8
⇒ Work done in 1 day by R = Work done in 1 day by (R + S + M) - Work done in 1 day by (S + M) = 5/8 - 1/4 = (5 - 2)/8 = 3/8
Number of days taken by R to do the job = Total work/Work done in 1 day by R = 1/(3/8) = (8/3) days