Simple interest


  1. At simple interest, a sum doubles after 20 years. The rate of interest per annum is ?









  1. View Hint View Answer Discuss in Forum

    Let sum = P, then SI = P and Time = 20 years
    ∴ Required rate = (100 x SI)/(P x T) = (100 x P) / (P x 20) = 5% per annum

    Correct Option: A

    Let sum = P, then SI = P and Time = 20 years
    ∴ Required rate = (100 x SI)/(P x T) = (100 x P) / (P x 20) = 5% per annum


  1. The simple interest at R% for R years will be Rs. R on a sum of ?









  1. View Hint View Answer Discuss in Forum

    Sum = (100 x SI) / (R x T)
    = (100 x R) / (R x R)

    Correct Option: C

    Sum = (100 x SI) / (R x T)
    = (100 x R) / (R x R)
    = Rs. 100/R



  1. A sum of money at simple interest amounts to Rs. 2240 in 2 years and Rs. 2600 in 5 years. The sum is ?









  1. View Hint View Answer Discuss in Forum

    S.I for 3 years = Rs. (2600 - 2240) = Rs . 360
    S.I for 2 years = Rs. (360/3 x 2) = Rs. 240

    Correct Option: B

    S.I for 3 years = Rs. (2600 - 2240) = Rs . 360
    S.I for 2 years = Rs. (360/3 x 2) = Rs. 240
    ∴ Required sum = Rs . (2240 - 240) = Rs. 2000


  1. At the certain rate of simple interest, a certain sum doubles itself in 10 years. It will treble itself in ?









  1. View Hint View Answer Discuss in Forum

    Let principal = P. Then, S. I = P. and Time = 10 years
    ∴ Required time = [(n - 1) x t] / (m - 1)

    Correct Option: B

    Let principal = P. Then, S. I = P. and Time = 10 years
    ∴ Required time = [(n - 1) x t] / (m - 1)
    = [(3 - 1) x 10] / (2 - 1)
    = 20 years



  1. A sum of money put at simple interest trebles itself in 15 years. The rate per cent per annum is ?









  1. View Hint View Answer Discuss in Forum

    Let principal = P
    Then, SI = 2P & Time = 15 years
    ∴ Required rate = (100 x SI) / (P x T) = (100 x 2P) / (P x 15)

    Correct Option: A

    Let principal = P
    Then, SI = 2P & Time = 15 years
    ∴ Required rate = (100 x SI) / (P x T) = (100 x 2P) / (P x 15) = 200/15 = 131/3 per annum