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 answers:
A) 10	B) 13	C) 14	D) 15	E) 16
Solution   Let the required number of hours per day be x.   Less persons, More days (Indirect Proportion)   More working hrs per days, Less days (Indirect Proportion)   ∴ 30 × 6 × x = 39 × 5 × 12 ⇔ x = 39x5x12/30x6 =x =13. Answer 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 ?