Question 799150
Add their rates of painting
Bob's rate: ( 1 house ) / ( 5 hrs )
Joe's rate: ( 1 house ) / 3 hrs )
Let {{{ t }}} = the time in hours for
them to paint the house together
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{{{ 1/5 + 1/3 = 1/t }}}
Multiply both sides by {{{ 15t }}}
{{{ 3t + 5t = 15 }}}
{{{ 8t = 15 }}}
{{{ t = 1.875 }}}
{{{ .875*60 }}} minutes
It will take them 1 hr and --- minutes
( you can do the above calculation )