Multiple choice

A sum of money becomes six times at simple interest. The rate of interest is $5\%$ per annum. At what rate per cent will it become twelve fold ?

  1. $7\%$ pa
  2. $9\%$ pa
  3. $11\%$ pa
  4. $13\%$ pa
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Simple interest formula: A = P(1 + RT). 6P = P(1 + R*T) => 5 = RT. If R=5%, then T=100 years. To become 12-fold, 12P = P(1 + R'*T). 11 = R'*100. R' = 11%.

AI explanation

Using the simple interest method, a sum becomes six times at 5 percent, meaning the principal equals the original sum and the interest equals five times the principal. The time taken is calculated as (500 divided by 5), which is 100 years. To become twelve fold, the interest must equal eleven times the principal, requiring 1100 percent interest over the same 100 years. The new rate is 1100 divided by 100, which equals 11 percent per annum. The result is 11 percent per annum.

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