Question 765113
It takes 4 workers 9 days to lay a stretch of road
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Half that number of workers will take twice as long, so
It takes 2 workers 18 days to lay a stretch of road
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3 times that number of workers will take 1/3 of that time, so
It takes 6 workers 6 days to lay a stretch of road
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You can also do an inverse variation:
{{{ 4 = k*( 1/9 ) }}}
{{{ k = 36 }}}
and
{{{ 6 = k*( 1/d ) }}}  ( {{{ d }}} is days to lay the road )
{{{ 6 = 36*( 1/d ) }}}
{{{ d = 36/6 }}}
{{{ d =  6 }}}