-- John takes 2 days to build a fence. He builds 1/2 of a fence each day.
-- Bill takes 5 days to build a fence. He builds 1/5 of a fence each day.
-- Working together, they build (1/2 + 1/5) of a fence each day.
Before we can add (1/2 + 1/5), we need a common denominator.
The least common multiple of 2 and 5 is 10.
1/2 = 5/10
1/5 = 2/10
(1/2 + 1/5) = (5/10 + 2/10) = 7/10 fence <==
Working together, they build at the rate of 7/10 fence per day.
==> Or 10/7 day per fence.
10/7 day = 1-3/7 day
If their work day is 8 hours, then 1-3/7 day is ...
1 day 3 hours 25 minutes 42.9 seconds of work per fence.