Question 770917
A's rate of working:
( 1 job ) / ( 15 days )
B's rate of working:
{ 1 job ) / ( 10 days )
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What fraction of the job did they get
done in 2 days? Let the fraction = {{{k}}}
{{{ 1/15 + 1/10 = k/2 }}}
Multiply both sides by {{{ 30 }}}
{{{ 2 + 3 = 15k }}}
{{{ k = 5/15 }}}
{{{ k = 1/3 }}}
That means there is 2/3 of the job left to finish
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A working alone:
Let {{{ t }}} = time in days to finish job
{{{ 1/15 = ( 2/3) / t }}}
{{{ t*( 1/15 ) = 2/3 }}}
{{{ t = 15*( 2/3 ) }}}
{{{ t = 10 }}} days
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The whole work was completed in {{{ 2 + 10 = 12 }}} days