Kevin has mowed 40% of the lawn. If he has been mowing for 20 minutes, how long will it take him to mow in a hour?

There are several vital information's that are given in the problem. The most vital information that is given in the problem is that Kevin mowed 40% of the lawn in 20 minutes. The thing that needs to be determined is the a mount of lawn that can be mowed in 1 hour.

Then

The amount of lawn mowed by Kevin in 20 minutes = 40 percent

The amount of lawn mowed by Kevin in 60 minutes = [ (40/20) * 60] percent

= 120 percent

So Kevin will mow 120% of the lawn in 1 hour.