Multiple choice

A sum of Rs. 500 borrowed at simple interest will double itself in 10 years. In how many years will it triple itself at the same rate of interest?

  1. 20 years

  2. 30 years

  3. 15 years

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Simple interest I = PRT/100. To double, I = P, so P = P*R*10/100, R = 10%. To triple, I = 2P, so 2P = P*10*T/100, T = 20 years.

AI explanation

A sum doubles in 10 years, meaning the simple interest earned equals the principal, so Rs. 500 of interest is earned on Rs. 500 in 10 years. Using the simple interest formula, R = (100 x SI) / (P x T), the rate is (100 x 500) / (500 x 10) = 10% per annum. To triple itself, the sum must earn interest equal to twice the principal, which is Rs. 1000. The required time is T = (100 x 1000) / (500 x 10) = 20 years. The correct answer is 20 years.

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