Compound Interest : Aptitude Test (65 Questions with Explanation)

  • 1. What would be the compound interest on Rs.7700/- at 15 ¼% per annum for 2 years compounded annually
A.) Rs.2725.75/-
B.) Rs.2527.57/-
C.) Rs.2227.57/-
D.) Rs.2520.57/-

Answer: Option 'B'

Principal = Rs. 7700/- 
time = 2 years 
rate = 15 ¼% 
Amount = P(1+R/100)n 
= 7700 × (1 + 61/(4 × 100)2) 
= 7700 × [(1 + 61/400)2] 
= 7700 × [(461/400)2)] 
= 7700 × 461/400 × 461/400 
= 7700 × 1.1525 × 1.1525 
= 7700 × 1.32825625 
= 10227.573125 
C.I = 10227.573125 - 7700 = 2527.57/-

  • 2. Certain sum becomes 3 times it self at compound interest in 10 years. In how many years it becomes 9 times?
A.) 25 years
B.) 27 years
C.) 30 years
D.) 20 years

Answer: Option 'D'

P(1 + R/100)10 = 3P 
=> P(1 + R/100)10 = 3 
Let P(1 + R/100)n = 9P 
=> (1 + R/100)n = 9 
=> 32 = [(1 + R/100)10]2 
=> (1 + R/100)n => (1 + R/100)20 
=> n = 20 Years.

  • 3. An amount at compound interest sums to Rs.17640/- in 2 years and to Rs.18522/- in 3 years at the same rate of interest. Find the rate percentage?
A.) 5%
B.) 6%
C.) 4%
D.) 10%

Answer: Option 'A'

The difference of two successive amounts must be the simple interest in 1 year on
the lower amount of money. 
S.I = 18522/- - 17640/- = Rs. 882/- 
Rate of interest = (882/17640) × (100/1) => 8820/1764 = 5% 
Principal = Amount/(1 + R/100)n 
= 17640/(1 + 5/100)2 
= 17640/(21/20 × 21/20) 
= 17640/(1.05 × 1.05) 
= 17640/1.1025 
= 16000

  • 4. Certain loan amount was repaid in two annual installments of Rs.1331/- each. If the rate of interest be 10% per annum Compounded annually the sum borrowed was?
A.) Rs.121/-
B.) Rs.2130/-
C.) Rs.2310/-
D.) Rs.1331/-

Answer: Option 'C'

Principal = (P.W of Rs. 1331/- due 1 year hence) + (P.W of Rs. 1331/- due 2 years hence) 
= [1331/(1 + 10/100) + 1331/(1 + 10/100)2
= [1331/(110/100) + 1331/(110/100 × 110/100)]
= 13310/11 + 133100/121 = 1210 + 1100 = Rs.2310/-

  • 5. The difference between the compound interest and simple interest on a certain sum of money at 5% per annum for 2 years is 45. Then the original sum is? 
A.) Rs.16000/-
B.) Rs.15000/-
C.) Rs.18000/-
D.) Rs.20000/-

Answer: Option 'C'

For 2 years = (1002D)/R2
= (1002 × 45)/(5 × 5) = (10000 × 45)/25 = Rs.18000/-