Question 964695
The rate of working for {{{ 4 }}} members is:
[ 1 job ] / ( 18 days ]
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{{{ 1 }}} member will take {{{ 4 }}} times as long
to finish the job, so the rate for {{{ 1 }}} member is:
[ 1 job ] / [ 72 days ]
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The rate for {{{ 9 }}} members would be {{{ 9 }}}  times
as fast as the rate for {{{ 1 }}} member, so the rate is:
{{{ 9*( 1/72 ) = 1/8 }}}, or
[ 1 job ] / [ 8 hrs ]
All 9 members of the crew take 8 hrs
to complete the same job