39 persons can construct 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? Options.
A) 10  B) 13  C) 14  D) 15  E) None of these
Explanation :   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   30 x 6 x x = 39 x 5 x 12   x = (39 x 5 x 12) /(30 x 6)   x = 13.   Answer : 13
<result>B</result>
39 persons can construct 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?