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# SIMPLE INTEREST & COMPOUND INTEREST SET1

Q.1 Rs. 4800 becomes Rs. 6000 in 4 yrs at a certain rate of C.I. What will be the sum after 12 yrs ?
A) Rs. 9375
B) Rs. 9475
C) Rs. 9575
D) Rs. 9675
Ans. A
Shortcut:
4800 [(6000)12/4 / (4800)12/4-1 ]Or 4800 * (6000)3 / (4800)2
Rs. 9375

Q.2 A sum of money doubles itself at C.I. in 15 yrs. In how many yrs will it become 8 times ?
A) 45 yrs
B) 46 yrs
C) 47 yrs
D) 48 yrs
Ans. A
P becomes 2p in 15 yrs
2p becomes 4p in next 4 yrs
4p becomes 8p in next 4 yrs
Therefore, 15+15+15 = 45yrs

Q.3 Man deposits Rs.5600 in a bank at 3 ¾% annual interest. After 6 months he withdraws Rs. 3200 together with the total interest till now & after the end of the year he withdraw the remaining money. How much does he get as interest ?
A) 150
B) 160
C) 155
D) 165
Ans. A
S.I. of Rs. 5600 for 6 months = 5600 * ½ * 15/4 / 100 = Rs.105
He withdraws Rs. 3200 together with interest, then remaining amount
= 5600 – 3200 = Rs. 2400
S.I. on Rs. 2400 at the rate of 15/4 for ½ year
=2400 * ½ * 15/4 / 100 = Rs.45
Therefore, total interest = 45 + 105 = 150

Q.4 Sum of money amounts to Rs. 944 in 3 years at S.I. If the rate of interest be raised by 25%, sum amounts to Rs. 980 during the same period. Find the sum & the rate of interest ?
A) 4%
B) 5%
C) 6%
D) 7%
Ans. C
980 – 944 = Rs. 36
25 % of interest = 36 * 100 / 25 = 144
Hence interest of three years = Rs. 144
Therefore, principal = 944 – 144 = Rs. 800/-
Rate = 144 * 100 / 800 * 3 = 6%
Hence profit = 132 ¼ – 100
= 32 ¼ %

Q.5 Simple interest on a certain sum of money for 3 years at 4% is Rs. 303.60. Find the compound interest on the same sum for the same period & at the same rate ?
A) Rs. 315.90
B) Rs. 316.90
C) Rs. 317.90
D) Rs. 318.90
Ans. A
P = 303.60 * 100 / 4 * 3 = Rs. 2530
C.I. = p [(1+ R/100)t – 1 ]= 2530 [(1 + 4/100)3 – 1 ]
Or 2530 [(26/25)3 – 1]2530 [1951 / 15625 ]
= Rs. 315.90