M and N can complete a job in 120 days and 180 days respectively. M started the job and after 60 days N joined M and they completed the remaining part of the job working together.In how many days was the job completed?

Options

A. 88
B. 84
C. 96
D. 82

Answer

C

Explanation

M works for the first 60 days. Part of the job completed in the first 60 days
`=60((1)/(120))=(1)/(2)`
Remaining part =1/2.This will be completed by M and N, part of the job completed by M and N in 1 day
`=(1)/(120)+(1)/(180)=(1)/(72)`
Time taken by them to complete the remaining part
`=((1)/(2))/((1)/(72))=36`days
`:.` The total time taken =96 days.