1.  The least number of complete years in which sum of money put out at 20% compound interest will be more than double 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.