Question 724068
Find the rate of one man.  Multiply that by 5.  The rate of each man is additive when any work together.


For 3 men working 8 hours to do the job, 1 man needs 3 times the time for the same amount of job; so 1 man works 24 hours for this job.


Five Men?  Amount of time is one-fifth of 24 hours, or {{{24/5}}} hours.


Note that this could also be done using rates of work in the form of jobs/time and can be easier for some people to analyze this way.  One would start by saying 3 men working together do the job at the rate of 1/8 jobs per hour...