Question 347781
Add their rates of mowing to get the rate mowing together
Jack's rate: 1 lawn/5 hrs
Marilyn's rate: 1 lawn/4 hrs
Rate working together = 1 lawn/x hrs
{{{1/5 + 1/4 = 1/x}}}
multiply both sides by {{{20x}}}
{{{4x + 5x = 20}}}
{{{9x = 20}}}
{{{x = 2.222}}} hrs
This is about 2 hrs and 13 min