ratio and proportn

Let the total no days to require to build the house with 45 men be X.
first 40 days, 45 men worked, so the total work done is 40*45
the job is finished 5 days ahead of 60 days, nothing but 60-5=55 days

so for 15 days 45+30 = 75 men worked.

Total work done =(40*45) + (15*75) = 45 men worked for X days,
45*X = (40*45) + (15*75)
solve for x, X will be 65. that means 45 men would have completed the job in 65 days. so 5 days more than planned.

Regards,
Kalyan.