Question

If it takes five men 20 hours to build a house how long would it take a man to do the job if they work at the same rate

Answer 1

It would take him 5 × 20 = 100 hrs

Answer 2

this problem can be solved by inverse rule of three.
5 men--------------------20 hours
1 man-------------------- x

5 men*20 hours=1 man*x
x=(5 men*20 hours) / 1 man=100 hours.

answer: 100 hours.