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

2 Answers
Mar 30, 2015

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#

Mar 30, 2015

(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#