Multiple choice

If any amount doubles itself in 5 years at the interest rate compounded annually then in how many years will it become eight times ?

  1. 18 years

  2. 21 years

  3. 24 years

  4. 15 years

  5. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

If an amount doubles in 5 years with compound interest, the relationship is 2 = (1+r)⁵, so (1+r)⁵ = 2. For eight times, we need (1+r)ⁿ = 8 = 2³ = [(1+r)⁵]³ = (1+r)¹⁵. Therefore n = 15 years. Option D is correct.

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