A work can be completed by N men in 15 days. 5 men leave the work after 3 days. The remaining work was completed in 18 days. What is the value of N?
Answer & explanation
Correct answer: option 3
Let the efficiency of 1 man be 'E'
Total work done by N men = N x E = 15NE
Total work done by N men in 3 days = 3NE
After 3 days 5 men left the work. Remaining workers = N - 5
The remaining work is completed in 18 days by (N - 5) workers,
⇒ 3NE + 18 x (N - 5) x E = 15 NE
⇒ 18(N - 5) = 12N
⇒ 18N - 90 = 12N
⇒ 6N = 90
⇒ N = 15.