Aditya, Vedus and Yuvraj alone can do a job for 6 weeks, 9 weeks and 12 weeks respectively. They work together for 2 weeks. Then, Aditya leaves the job. Vedus leaves the job a week earlier to the completion of the work.The job would be completed in:
4 weeks
5 weeks
7 weeks
None
Aditya's 1 week work = 1/6
Vedus's = 1/9
Yuvraj's = 1/12
Step 1 : work done for first 2 weeks
= 2 x (1/6 + 1/9 + 1/12 )
LCM of 6,9,12 = 36
= 2 x (6+4+3)/36 = 2 x 13/36 = 26/36
Remaining work = 1 - 26/36 = 10/36
Step 2 : after 2 weeks aditya leaves .vedus and yuvraj work together
Let total time = x weeks
So vedus , works ( x - 3 ) weeks ( he leaves 1 week before ends )
Yuvraj works full ( x - 2 ) weeks
Work done after Aditya left :
= ( x - 3 ) x 1/9 + (x-2) x 1/12
= (4x - 10 )/36
This must equal to remaining work:
(4x - 10 )/36 = 10/36
4x - 10 = 10
4x = 20
x = 5
Answer : option 2 - 5 weeks