Compound Interest


  1. The difference between the compound interest and the simple interest on a certain sum at 5% per annum for 2 years is Rs. 1.50. The sum is ?









  1. View Hint View Answer Discuss in Forum

    Let the sum be Rs. 100 then,
    S.I.= Rs.(100 x 5 x 2)/100 =Rs.10
    C.l.= Rs.[100 x (1 +5/100)2] =Rs.41/4

    ∴ difference between C.I. and S.I. = Rs. (41/4-10) = Re.0.25

    Correct Option: A

    Let the sum be Rs. 100 then,
    S.I.= Rs.(100 x 5 x 2)/100 =Rs.10
    C.l.= Rs.[100 x (1 +5/100)2] =Rs.41/4

    ∴ difference between C.I. and S.I. = Rs. (41/4-10) = Re.0.25

    ⇒ 0.25 : 1.50 : : 100 : P
    ∴ P = (1.50 x 100) / 0.25 = Rs. 600


  1. The simple interest on a certain sum for 2 years at 10% per annum is Rs.90. The corresponding compound interest is?









  1. View Hint View Answer Discuss in Forum

    Principle = (100 x interest) / (time x rate)
    ⇒ Sum = (100 x 90) / (2 x 10) = Rs. 450

    Correct Option: C

    Principle = (100 x interest) / (time x rate)
    ⇒ Sum = (100 x 90) / (2 x 10) = Rs. 450

    C.I. =Rs.[ 450 x (1 + 10/100)2 - 450] = Rs. 94.50



  1. What is the principle amount which earns Rs. 132 as compound interest for the second years at 10% per annum ?









  1. View Hint View Answer Discuss in Forum

    Let P the principle at the end of first year.
    Then (P x 10 x 1)/100 =132
    ⇒ P =1320

    Let Q be the original principle
    Then, Q + (Q x 10 x 1)/100 =1320
    ⇒ Q =1200

    Correct Option: B

    Let P the principle at the end of first year.
    Then (P x 10 x 1)/100 =132
    ⇒ P =1320

    Let Q be the original principle
    Then, Q + (Q x 10 x 1)/100 =1320
    ⇒ Q =1200


  1. Simple interest on a sum at 4% per annum for 2 years is Rs.80. The compound interest on the same sum for the same period is ?









  1. View Hint View Answer Discuss in Forum

    principle = (interest x 100) / (time x rate)
    = Rs. (100 x 80)/(4 x 2) = Rs. 1000

    ∴ C.I. =Rs.[{1000 x (1 + 4/100)2 - 1000}]

    Correct Option: A

    principle = (interest x 100) / (time x rate)
    = Rs. (100 x 80)/(4 x 2) = Rs. 1000

    ∴ C.I. =Rs.[{1000 x (1 + 4/100)2 - 1000}]
    = Rs. 81.60



  1. The least number of complete years in which a sum of money put out at 20% compound interest will be more than doubled is ?









  1. View Hint View Answer Discuss in Forum

    ∵ P x (1 + 20/100)t > 2P
    ⇒ (6/5)n > 2

    Correct Option: B

    ∵ P x (1 + 20/100)t > 2P
    ⇒ (6/5)n > 2
    Now, (6/5) x (6/5) x (6/5) x (6/5) > 2
    ⇒ 1296/615 > 2
    ∴ t = 4 years