Multiple choice

In a certain time a sum becomes 4 times as the rate of 5% per annum. At what rate of simple interest the same sum becomes 8 times in the same duration ?

  1. 12.23 %

  2. 11.35%

  3. 11.66%

  4. 12.35%
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The sum becomes 4 times in t years at 5% SI, meaning interest is 3P. 3P = P * 0.05 * t, so t = 60 years. To become 8 times, interest must be 7P. 7P = P * R * 60 / 100, so R = 700 / 60 = 11.66%.

AI explanation

If a sum becomes 4 times at 5% simple interest, the interest earned is 3 times the principal, so using the formula T = (100 * SI) / (P * R), the time is T = (100 * 3P) / (P * 5) = 60 years. To become 8 times in the same 60-year duration, the interest must be 7 times the principal, meaning the required rate is R = (100 * 7P) / (P * 60). This calculates to 700 / 60 = 11.66%. The rate is 11.66%.

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