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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. Rs. 600
    2. Rs. 500
    3. Rs. 400
    4. Rs. 300
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    Let the sum be Rs . 100 then
    S.I. = Rs.(100 x 5 x 2/100)= Rs. 10
    C.I = Rs. [{100 x (1 + 5/100)2} - 100] = Rs. 41/4

    ∴ Difference between C.I and S.I = Rs. (41/4 - 10) = Re. 0.25
    ⇒ 0.25 : 150 : : 100 : P
    ∴ P = (1.50 x 100) / 0.25 = Rs. 600

    Correct Option: A

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

    ∴ Difference between C.I and S.I = Rs. (41/4 - 10) = Re. 0.25
    ⇒ 0.25 : 150 : : 100 : P
    ∴ P = (1.50 x 100) / 0.25 = Rs. 600

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  1. If the compound interest on a certain sum for 2 years at 12.5% per annum is 170, the simple interest is ?
    1. Rs. 150
    2. Rs. 152.50
    3. Rs. 160
    4. Rs. 162.50
  1. View Hint | View Answer | Workspace | Discuss In Forum | Report

    Let the principle is P
    so compound interest = p x ( 1 + (12.5/100))sup>2 - p = 170
    ⇒ p x (112.5/100) x (112.5/100) - p = 170
    ⇒ P [ 12656.25 - 10000 ] = 170 x 10000
    ∴ p = (170 x 10000) / 2656.25

    Simple interest SI = (P x T x R )/100
    = [{(170 x 10000) / 2656.25} x 2 x 12.5] / 100
    = 160

    Correct Option: C

    Let the principle is P
    so compound interest = p x ( 1 + (12.5/100))sup>2 - p = 170
    ⇒ p x (112.5/100) x (112.5/100) - p = 170
    ⇒ P [ 12656.25 - 10000 ] = 170 x 10000
    ∴ p = (170 x 10000) / 2656.25

    Simple interest SI = (P x T x R )/100
    = [{(170 x 10000) / 2656.25} x 2 x 12.5] / 100
    = 160

    Report

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  1. A sum amounts to Rs. 1352 in 2 years at 4% compound interest.The sum is ?
    1. Rs. 1300
    2. Rs. 1250
    3. Rs. 1260
    4. Rs. 1200
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    Let the sum be P.
    Then, 1352 = P(1 +4/100)2

    Correct Option: B

    Let the sum be P.
    Then, 1352 = P(1 +4/100)2
    ⇒ 1352 = P x 26/25 x 26/25
    ⇒ P = (1352 x 25 x 25) / (26 x 26) = 1250
    ∴ Principal = Rs. 1250

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  1. Rs. 800 at 5% per annum compound interest will amount to Rs. 882 in ?
    1. 1 years
    2. 2 years
    3. 3 years
    4. 4 years
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    Let time be t years
    ∵ 882 = 800( 1 +5/1000)t
    ⇒ 882/800 = (21/20)t

    Correct Option: B

    Let time be t years
    ∵ 882 = 800( 1 +5/1000)t
    ⇒ 882/800 = (21/20)t
    ⇒ (21/20)2 = (21/20)t
    ⇒ t =2
    ∴ Time = 2years

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  1. The compound interest on Rs. 2800 for 11/2 years at 10% per annum is ?
    1. Rs. 441.35
    2. Rs. 436.75
    3. Rs. 434
    4. Rs. 420
  1. View Hint | View Answer | Workspace | Discuss In Forum | Report

    ∵ Final Amount = Rs.[2800 x (1 + 10/100) x (1 +5/100)]
    = Rs. [ 2800 x 11/10 x 21/20 ]
    = Rs. 3234

    Correct Option: C

    ∵ Final Amount = Rs.[2800 x (1 + 10/100) x (1 +5/100)]
    = Rs. [ 2800 x 11/10 x 21/20 ]
    = Rs. 3234

    ∴ Required C.I. = Rs.(3234 - 2800) = Rs .434

    Report

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