Multiple choice

Rs.100 doubled in 5 years when compounded annually. How many more years will it take to get Another Rs.200 compound interest?

  1. 10 years

  2. 5 years

  3. 7.5 years

  4. 15 years
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let P be principal and r be rate. P(1+r)^5 = 2P, so (1+r)^5 = 2. To reach 4P (double again), we need P(1+r)^n = 4P, so (1+r)^n = 4 = 2². Since (1+r)^5 = 2, we need n = 10 years total. Already 5 years have passed, so 5 more years needed. Option B is correct.

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