27 men can dig a well in 20 days working 5 hours a day. They start digging it. After 4 days, 12 men leave. How hourse a day should the remaining men work to complete digging it by the scheduled date ?

Options

A. 6
B. 8
C. 10
D. 9

Answer

D

Explanation

Let the requred number of hours pe day b h.
Let the work done by each man be 1 unit/hr /
The time for which 27 men worked in the first our days =(5)(4) hours =20 hours
Work complete in the first 4 days `=(27)(1)(20)` units =540 units
Renaining in time `=(20-4) (h)` hours =16 h hours.
Completed in the remaining time `=(27-12)(1)(16h)` units =240 h units
Total time taken `=(5)(20)` hours=100 hours
Total work `=(27)(1)(100)` units =2700 units `2700+540+240h`
9 hours