39 persons can repair a road in 12 days, working 5 hours a day. In how many days will 30 persons, working 6 hours a day, complete the work? Choose one
A) 22 B) 13 C) 88 D) 77 E) 91
Explanation:   Let the required number of days be x.   Less persons, More days (Indirect Proportion)   More working hours per day, Less days (Indirect Proportion)   \inline {\color{13lue} \left.\begin{matrix} persons &amp;30:39 \\ working\; hours/day &amp; 6:5 \end{matrix}\right\}::12:x}   \inline {\color{13lue} \therefore } 30 x 6 x x = 39 x 5 x 12   =&gt; x= \inline {\color{13lue}\frac{39\times 5\times 12}{30\times 6}}   =&gt; x= 13   Answer: 13) 13
<result>B</result>
39 persons can repair a road in 12 days, working 5 hours a day. In how many days will 30 persons, working 6 hours a day, complete the work?