Question 734255
Add their rates of working to get their rate working
together.
Let {{{ r }}} = Sister's rate in ( jobs / hr )
{{{ 2r }}} = Rick's rate in ( jobs / hr )
given:
{{{ r + 2r = 1/8 }}}
The 1/8 means ( 1 job / 8 hrs )
{{{ 3r = 1/8 }}}
{{{ r = 1/24 }}}
{{{ 2r = 2/24 }}}
Rick could do 2 jobs in 24 hrs, which is the same as
{{{ 2/24 = 1/12 }}} 1 job in 12 hrs
So, he could do the job by himself in 12 hrs
check answer:
{{{ r + 2r = 1/8 }}}
{{{ 1/24 + 1/12 = 1/8 }}}
{{{ 1/24 + 2/24 = 3/24 }}}
{{{ 3/24 = 3/24 }}}
OK