If 5 machines can produce 20 units in 10 hours, how long would it take 10 to produce 60 units? Answers:
A) 9 B) 10 C) 15 D) 25 E) 30

Rationale: "5 machines would produce 60 units in 30 hours . increasing the amount of machines by 2 would mean dividing 30 hours by 2 . 30 / 2 = 15 answer : c"
Answer: C