twelve men take 6 hours to finish a piece of work. after the 12 men have worked for 1 hour, the contractor decides to call in 8 more men so that the work can be completed earlier. how many more hours would 20 men take to compete the remaining work?
the job is 12*6 = 72 man-hours of work.
In 1 hour, the 12 men have done 1/6 of the work, leaving 60 man-hours to do.
That will take 20 men 3 hours to finish up.
To solve this problem, we need to understand the concept of man-hours. A man-hour is the amount of work one person can complete in one hour. In the given scenario, we are told that twelve men take 6 hours to finish the work, which means the total man-hours required for the job is 12 men * 6 hours = 72 man-hours.
Now, after working for 1 hour, the 12 men have completed 12 men * 1 hour = 12 man-hours of work. So, the remaining work is 72 man-hours - 12 man-hours = 60 man-hours.
After calling in 8 more men, the total number of workers becomes 12 men + 8 men = 20 men. Now we need to determine how many hours it would take for these 20 men to complete the remaining work of 60 man-hours.
To find the answer, we can use the concept of man-hours again. We know that the total man-hours for the remaining work is 60 man-hours and the number of men is 20. Therefore, the time taken to complete the remaining work is 60 man-hours / 20 men = 3 hours.
Hence, it would take an additional 3 hours for the 20 men to complete the remaining work.