The least number of complete years in which a sum of money put out at 20% compound interest will be more than doubled is:

Question:
The least number of complete years in which a sum of money put out at 20% compound interest will be more than doubled is:

[A].

3

[B].

4

[C].

5

[D].

6

Answer: Option B

Explanation:

P 1 + 20 n > 2P         6 n > 2.
100 5
Now, 6 x 6 x 6 x 6 > 2.
5 5 5 5

So, n = 4 years.