Respuesta :

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.
Divyankasc
It would take him 5 × 20 = 100 hrs