Question 668250
Add their rates of working
Jacob's rate is ( 1 installation ) / ( 5 hrs )
Aiden's rate is ( 1 installation ) / ( 20 hrs )
Let {{{ 1/t }}} = the rate working together
{{{ 1/5 + 1/20 = 1/t }}}
Multiply both sides bt {{{ 20t }}}
{{{ 4t + t = 20 }}}
{{{ 5t = 20 }}}
{{{ t = 4 }}}
It takes the 2 men 4 hrs working together