Twelve men take 6 hours to finish a piece of work. After the 12 men have worked for 1 hour, the contractor decides to call in 8 more men. How many more hours would 20 men take to complete the remaining work?

12 men took to 6 hours to complete the work.

It means there is 12 x 6= 72 units of work

Now 12men done work for one hour. So 12 x 1 =12 units of work completed.

Remaining work = 72-12= 60 units

Now the no of men=12+8= 20

So 60 units of work have to complete by 20 men

Therefore 60/20= 3 hours