Question

a man can do a job as fast as his two sons working together if one son does the job in 3 hours and the other in 6 hours how many hours does it take the men to do the job

Answer 1

if his one son can do work in 6 hour
then work he can do in 1 hour = 1/6
his other son can do work in 3 hour
work he can do in 1 hour = 1/3
so man can complete work in = 1/3 + 1/6
=1/2
so man can do work in 2 hour