IBPS Clerk Prelims Model Paper 8

Do not get confused by the distractions given in the problem. 10 men and 10 days mean 100 mandays are required to clean 10 floors.
This means that 1 floor requires 10 man-days.
Hence, 8 floors will require 80 man-days to clean.
Therefore, 10 days are required to clean 8 floors.