Question 828316
Shawn's rate is ( 1 job ) / ( 4 hrs )
Ellie's rate is ( 1 job ) / ( 6 hrs )
Let {{{ t }}} = time for them to do the job together
{{{ 1/4 + 1/6 = 1/t }}}
Multiply both sides by {{{ 12t }}}
{{{ 3t + 2t = 12 }}}
{{{ 5t = 12 }}}
{{{ t = 2.4 }}} hrs
The foreman is wrong