Question 1012188
Add their rates of working to get their
rate of working together
Rob's rate:
[ 1 attic cleaned ] / [ 9 hrs ]
Huong's rate:
[ 1 attic cleaned ] / [ 15 hrs ]
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Let their rate working together =
[ 1 attic cleaned ] / [ t hrs ]
{{{ 1/9 + 1/15 = 1/t }}}
Multiply both sides by {{{ 45t }}}
{{{ 5t + 3t = 45 }}}
{{{ 8t = 45 }}}
{{{ t = 5.625 }}}
and
{{{ .625*60 = 37.5 }}}
Working together, it will take them
5 hrs 37 min 30 sec