P(1 + 20/100)n > 2P or (6/5)n > 2
Now, (6/5 * 6/5 * 6/5 * 6/5) > 2. So, n = 4 years.
This justifies what answer for what question? Q & A:
The least number of complete years in which a sum of money put out at 20% C.I. will be more than doubled is?
Options:
(A) 3
(B) 4
(C) 5
(D) 6
(E) 7
(B)