Question 1020353
What fraction of the job does A
get done in 2 hrs?
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A's rate of working:
[ 1 chair ] / [ 6 hrs ]
{{{ ( 1/6 )*2 = 1/3 }}}
That means 2/3 of the chair remains
to be built
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B's rate of working:
[ 1 chair ] / [ 9 hrs ]
Let {{{ t }}} = time in hrs for them to
finish the chair working together
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Add their rates of working to get
rate working together
{{{ 1/6 + 1/9 = ( 2/3) / t }}}
{{{ 1/6 + 1/9 = 2/(3t) }}}
Multiply both sides by {{{ 18t }}}
{{{ 3t + 2t = 12 }}}
{{{ 5t = 12 }}}
{{{ t = 12/5 }}} hrs
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check answer:
{{{ 1/6 + 1/9 = ( 2/3) / t }}}
{{{ 1/6 + 1/9 = ( 2/3) /(12/5) }}}
{{{ 3/18 + 2/18 = (2/3)*(5/12) }}}
{{{ 5/18 = 10/36 }}}
{{{ 5/18 = 5/18 }}}
OK