Question 1006967
it sounds like there is 5 hrs ( 8 AM to 1 PM )
when only machine A is making paper clips
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{{{ 1500 }}} paper clips /hr is A's rate of making them
{{{ 2500 }}} paper cips / hr is B's rate of making them
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What part of the order does machine A get done
in 5 hrs working alone?
{{{ 1500*5 = 7500 }}} paper clips
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That leaves {{{ 23500 - 7500 = 16000 }}}
left to be made
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Let {{{ t }}} = the number of hrs past 1PM when both
machines working together will finish the order
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Add their rates of working to get their rate  working together
Their rate working together is:
[ 16000 paper clips ] / [ t hrs ]
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{{{ 1500 + 2500 = 16000/t }}}
( note that I am adding rates to get a rate )
{{{ 4000t = 16000 }}}
{{{ t = 4 }}} hrs
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1 PM + 4 hrs = 5 PM when the order will be finished