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?  Answers
A) 9	B) 12	C) 10	D) 13	E) 14
Explanation :   Let the required number of days be x   More persons, less days (indirect proportion)   More hours, less days (indirect proportion)   ⇒ 39 × 5 × 12 = 30 × 6 × x   ⇒ 39 × 5 × 2 = 30 × x   ⇒ 39 = 3 × x   ⇒ x = 13. Answer : Option 13
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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?