If 80 lamps can be lighted 5 hours per day for 10 days for Rs. 21.25,then the number of lamps which can be lighted 4 hours daily for 30days for Rs. 76.50, is?
Choose the correct choice from the following answers: A) 100 B) 110 C) 120 D) 130 E) none of these

Rationale: explanation : ( hrs / day 4 : 5 ) : ( money 21.25 : 76.50 ) : ( days 30 : 10 ) : : 80 : x 4 * 21.25 * 30 * x = 5 * 76.50 * 10 * 80 so x = 120 answer : c
Answer: C