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Discussion

  1. If a certain sum is doubled in 8 yr on simple interest, in how many year will it be four times?
    1. 24 yr
    2. 16 yr
    3. 32 yr
    4. 12 yr
  1. Correct Option: A

    Let the sum be Rs 'y' , so amount = 2y
    Simple interest =Rs y
    Let R be the rate of interest,
    R= (100 x SI)/(P x T) = (100 x y) / (y x 8) = 12.5 %
    where SI= Simple Interest
    P = Principal
    T = Time

    now, the needed amount = Rs 4y
    since SI = Rs (4x-x)= Rs 3y
    since T= (100 x SI)/(P x R)
    = (100 x 3y )/(y x 125)= 24 yr


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