Question 1154934
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The new machine makes  {{{1/6}}}  of the job per hour.


The old machine makes  {{{1/16}}}  of the job per hour.


3 new machines and 4 old machines do  {{{3/6}}} + {{{4/16}}}  of the job per hour.


    {{{3/6}}} + {{{4/16}}} = {{{1/2}}} + {{{1/4}}} = {{{3/4}}} of the job per hour.


Hence, it will take  {{{4/3}}} hours to complete the job,  or  {{{1}}}{{{1/3}}} hours = 1 hour and 20 minutes.   <U>ANSWER</U>
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Solved.