Question 992308
What fraction of the job did Tammy get
done in 4 hrs?
[ fraction of job ] = [ her rate of working ] x [ hrs worked ]
{{{ ( 1/24 )*4 = 1/6 }}}
That means there is {{{ 5/6 }}} of the job left to do
when Cheryl joined her
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Add their rates of working to get their
rate working together
Let {{{ t }}} = time ime hrs for the both of them
to do {{{ 5/6 }}} of the job
{{{ 1/24 + 1/28 = (( 5/6 ))/t }}}
Multiply both sides by {{{ 2 }}}
{{{ 1/12 + 1/14 = (( 5/3 ))/t }}}
Multiply both sides by {{{ 84t }}}
{{{ 7t + 6t = 140 }}}
{{{ 13t = 140 }}}
{{{ t =10.77 }}}
It takes them 10.77 hrs to finish the job working together
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check:
{{{ 1/24 + 1/28 = (( 5/6 ))/t }}}
{{{ 1/24 + 1/28 = (( 5/6 ))/10.77 }}}
{{{ 1/24 + 1/28 = 5/64,62 }}}
{{{ .041667 + .035714 = .077375 }}}
{{{ .077381 = .077375 }}}
error due to rounding off, I think
Recheck my math