If eight men can dig a hole in 4 hours, how long will take the five men to dig the same hole?
You use the proportion (inversely proportionality)
if n° of men decreases
Time must increase
(Assuming the men don't get in each others' way)
if 8 men can dig a hole in 4 hours
the hole represents
5 men can complete 32 man-hours of work in