Question 690740
The rate  of harvesting for the 2 harvesters working together  is ( 1 field ) / ( 1 hr )
The rate of harvesting for the 1st harvester is ( 1 field ( / ( 1.5 hrs )
Let {{{ t }}} = the time in hrs for the 2nd harvester working  alone
The 2nd harvester's rate would be ( 1 field ) / ( t hrs )
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Add their rates to get their rate working together
{{{ 1/1.5 + 1/t = 1/1 }}}
{{{ 2/3 + 1/t = 1 }}}
Multiply both sides by {{{ 3t }}}
{{{ 2t + 3 = 3t }}}
{{{ t = 3 }}}
It takes 3 hrs for the 2nd harvester working alone
to harvest the field