Simple Interest

1.A sum of money at simple interest amounts to Rs. 815 in 3 years and to Rs. 854 in 4 years. The sum is: A)658 B)798 C)698 D)898 Answer : Option C Explanation: S.I. for 1 year = Rs. (854 - 815) = Rs. 39. S.I. for 3 years = Rs.(39 x 3) = Rs. 117. Principal = Rs. (815 - 117) = Rs. 698. 2. What will be the ratio of simple interest earned by certain amount at the same rate of interest for 5 years and that for 15 years? A)1:4 B)1:5 C)1:6 D)1:3 Answer : Option D Explanation: Simple Interest = PRT/100 Here Principal(P) and Rate of Interest (R) are constants Hence, Simple Interest ∝ T Required Ratio = Simple Interest for 5 years/Simple Interest for 15 years=T1/T2=5/15=1/3=1:3 3.A sum of money doubles in 12 years. In how many years, it will treble at S.I. A)25 B)24 C)26 D)28 Answer : Option B Explanation: Simple Interest, SI = PRT/100 i.e, SI ∝ T when rate(R) and principal (P) are constants Let x be the sum of money and which will treble in n years (Please note that when the money doubles, simple interest is 2x - x = x and when the money trebles, simple interest is 3x - x = 2x) (2x-x) ∝ 12 => x ∝ 12 -------------(1) (3x-x) ∝ n => 2x ∝ n -------------(2) From (1) and (2), x/2x=12/n 1/2=12/n⇒n = 24 years 4.The interest on a certain deposit at 5% per annum is Rs. 101.20 in one year. How much will the additional interest in one year be on the same deposit at 6% per annum? A)20.24 B)21.24 C)22.24 D)23.24 Answer : Option A Explanation: Principal, P = 100ŨSI/RT=100Ũ101.20/5Ũ1=20Ũ101.20=Rs. 2024 Simple Interest for Rs.2024 at 6% per annum for 1 year, SI = 2024Ũ6Ũ1/100=121.44 Additional Interest = Rs.121.44 - Rs.101.20 = Rs.20.24

« 1 2 3 »