it takes 8 men 11h40min to complete a task. If 2 out of 8 men leave after working for 1 hour, how long will it take for the remaining 6 men to complete the tast at the same rate?

Answer 1

8 * 11 2/3 = 93 1/3 man-hours

after 8 man-hr, 6 men must complete the remaining 85 1/3 man-hr

85 1/3 / 6 = ?

Answer 2

11h 40min = 700 minutes
So, each man does 1/5600 of the job in a minute

8 men working for 60 minutes complete 8*60/5600 = 3/35 of the job.

The remaining 6 men have to do 32/35 of the job, so it will take 8/6 as long as the full contingent of 8 men. The time is thus

8/6 * 32/35 * 700 = 1280/3 minutes = 7h6'40"

Answer 3

Better go with Scott. I seem to have lost a factor of 2 somewhere. 7 hours is clearly not long enough for a smaller crew to do almost the whole thing.

Answer 4

Thanks Scott and Steve
Yes, I think Scott I understood
and the answer is 14h 13 1/3min