Question 97737
Combined rate = (1 lawn / 2 hrs) + (1 lawn / 4 hrs)
{{{1/2 + 1/4 = 2/4 + 1/4}}}
{{{2/4 + 1/4 = 3/4}}}
This says together they can mow 3 lawns in 4 hours
divide top and bottom by 3
{{{(3/3) / (4/3) = 1 / (4/3)}}}
So, together, they can mow 1 lawn in 4/3 of an hour or 1 hour 20 minutes