Question 1198709
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With two reapers operating, a field can be harvested in 1 h. 
If only the newer reaper is used, the crop can be harvested in 1.5 h. 
How long would it take to harvest the field using only the older reaper?
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<pre>
The combined rate of work of two reapers is {{{1_field/1_hour}}} = 1 job per hour.


The individual rate of work of the new reaper is  

    1_field/1.5_hours = {{{1/1.5}}} = {{{1/((3/2))}}} = {{{2/3}}} of the job per hour.


Hence, the rate of work of the old reaper is 1 - 2/3 = 1/3 of the job per jour.


It means that the field can be harvested in 3 hours, if only old reaper is used.


<U>ANSWER</U>.  3 hours.
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Solved.