Question

If eight men can dig a hole in 4 hours, how long will take the five men to dig the same hole?

Answer 1

6.4 hours;
You use the proportion (inversely proportionality)
if n° of men decreases `8->5`
Time must increase `4->x` so inverting:
`8/5=x/4`
`x=32/5=6.4`

Answer 2

(Assuming the men don't get in each others' way)

if 8 men can dig a hole in 4 hours
the hole represents `8xx4 = 32` man-hours of work.

5 men can complete 32 man-hours of work in
`(32 cancel(man) hours)/(5 cancel(men)) = 6.4 hours`