The workers paved at a rate of 2/15 miles per 20 minutes. Now, we need to figure out how far they went in 60 minutes. Since 60 minutes is three times as large as 20 minutes, they will go three times as far. This is equal to 6/15 miles in one hour.
Now, we need to simplify the fraction. We do this by dividing both the numerator and denominator by 3. This equals 2/5. So, in one hour, the workers paved 2/5 of a mile.