It takes one man one day to dig a 2m x 2m x 2m hole How long does it take 3 men working at the same rate to dig a 4m x 4m x 4m hole?

The rate for one man to finish a 2mx2mx2m whole is...

1 man = 8m3 per day

At the same rate three men can each do a 2mx2mx2m whole. This is how much they altogether can do in one day.

3 men = 24m3 per day

The whole they have to dig is this size.

4mx4mx4m which is 64m3

Since three men can do 24m3 per day it will take them 2 days and 16 hours to dig a 64m3 hole.