Question 1078031
Kim's rate of working:
[ 1 garage door ] / [ 2 hrs ]
Jim's rate of working:
[ 1 garage door ] / [ 1 hr ]
Let {{{ t }}} = their time in hrs to paint the door
if they work together
Their rate working together:
[ 1 garage door ] / [ t hrs ]
-----------------------------
Add their rates of working to get their
rate working together
{{{ 1/2 + 1/1 = 1/t }}}
Multiply both sides by {{{ 2t }}}
{{{ t + 2t = 2 }}}
{{{ 3t = 2 }}}
{{{ t = 2/3 }}} hrs
-------------------
Convert this result to minutes
{{{ (2/3)*60 = 40 }}}
It will take them 40 minutes to paint the 
door if they work together