Multiple choice

In how much time will a sum of money at simple interest triple itself at the rate of $15\%$ per annum?

  1. $15$
  2. $10$
  3. $13.9$
  4. $13.3$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For simple interest, A = P(1 + rt/100). If A = 3P, then 3P = P(1 + 15t/100). 2 = 15t/100. t = 200/15 = 13.33 years.

AI explanation

To triple a sum at simple interest, the interest earned must equal twice the principal. Using the formula Time equals Interest divided by (Principal times Rate), we get Time equals 2 times Principal divided by (Principal times 0.15). This simplifies to 2 divided by 0.15, which gives a time of 13.3 years.

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