Compound-Interest questions : Quantitative Aptitude

  • 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/-



  • 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.



  • 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

    Thus the principal is Rs.16000/- and the rate of interest is 5%



  • 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/-



  • 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/-




Quantitative Aptitude Topics


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