39 persons can repair a road in 12 days, working 5 hours a day. In how many days will 15 persons, working 6 hours a day, complete the work? Pick
A) 10
B) 13
C) 14
D) 26
E) 16

Rationale: "let the required number of days be x . less persons , more days ( indirect proportion ) more working hours per day , less days ( indirect proportion ) persons 15 : 39 : : 12 : x working hours / day 6 : 5 15 x 6 x x = 39 x 5 x 12 x = ( 39 x 5 x 12 ) / ( 15 x 6 ) x = 26 . answer : d"
Answer: D