1) A sum of money invested at compound interest amounts in 3 years to Rs.2400 and in 4 years to Rs.2520. The rate of interest is A) 5% B) 6% C) 10% D) 12% E) 8% Answer: Option AExplanation:S.I. for 1 year =2520−2400 =120 P=2400 Rate % =120×1002400×1 = 5%