imo:5

The project required 10*110 = 1,100 man-days

so whatever happens has to equal 1100 to complete the project

we are told that of the first 60 days there were 5 days of rain, so:

55*10 + 5*0 = 550 (half way there)

then we hire 6 people so up to 16 employees and work until day 100. Let's assume there is NO rain, then they would have:

40*16 = 640

but since the job only needed 550 to complete and we have 16 ppl on board then:

(640-550)/16 = 90/16 ~ 5.6 ish

so there must have been at least 5 days of rain though 6 is too much (they would have needed MORE time)... Perhaps they busied themselves by whistling at scantily-clad women for ~0.6 days

Hope that helps

ya i was having trouble with the last part as i rounded it to 6..its pretty tricky..does it mean that if the 5.6 goes to 6 it means it rained for MORE days n' so the workers would take MORE than 100 days to complete?Thats the reason we are rounding down?