A contractor employs 15 men to complete a work in 24 days, working 8 hours per day. After six days, he adds five more men but also reduces the working hours to six per day from the seventh day onwards. If all men work with the same efficiency throughout, how many more days will be required to finish the remaining work?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 18.
Total work = 15 × 24 × 8 = 2880 man-hours
Work done in 6 days = 15 × 6 × 8 = 720 man-hours
Remaining work = 2880 - 720 = 2160 man-hours
New total man = 15 + 5 = 20
New daily man-hours = 20 × 6 = 120
Time required = 2160/120 = 18 days