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 the correct choice from the following:
A) 10
B) 13
C) 14
D) 15
E) 12
Let the required number of days be x.   Less persons, More days (Indirect Proportion)   More working hours per day, Less days (Indirect Proportion)   Persons 30	:	39 :: 12 : x   Working hours/day	6	:	5   Therefore 30 x 6 x x = 39 x 5 x 12   =&gt; x =(39 x 5 x 12)/(30 x 6)   =&gt; x = 13.   Correct answer is 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?