Question 888578
Trisha's rate:
( 1 lawn / 40 min )
Joe's rate:
( 1 lawn / 15 min )
Add their rates of mowing to get
their rate mowing together
Let {{{ t }}} = time in minutes to mow
lawn
{{{ 1/40 + 1/15 = 1/t }}}
Multiply both sides by {{{ 120t }}}
{{{ 3t + 8t = 120 }}}
{{{ 11t = 120 }}}
{{{ t = 10.91 }}}
Working together, it will take them 11 minutes