Question 577635
Add their rates of mowing to get thir
rate working together
Chris's rate: ( 1 lawn ) / ( 2 hrs, 23 min )
Jim's rate: ( 1 lawn ) / ( 3 hrs 15 min )
Let {{{ t }}} = time in minutes for them
to mow lawn together
------------------
{{{ 2*60 + 23 = 143 }}}
{{{ 3*60 + 15 = 195 }}}
{{{ 1/143 + 1/195 = 1/t }}}
Multiply both sides by {{{ 143*195*t }}}
{{{ 195t + 143t = 143*195 }}}
{{{ 338t = 27885 }}}
{{{ t = 27885/338 }}}
{{{ t = 82.5 }}}
{{{ 82.5 - 60 = 22.5 }}}
Working together, it takes them 1 hr and 22.5 min
check:
{{{ 1/143 + 1/195 = 1/82.5 }}}
{{{ .006993 + .0051282 = .0121212 }}}
{{{ .0121212 = .0121212 }}}
OK