A sum doubles itself in 8 years at simple interest. What is the rate?
A
10%
B
12.5%
C
15%
D
20%
Correct Answer: Option B — 12.5%
Explanation:
If principal = P then SI = P (since it doubles). SI = P×R×8/100 → P = P×R×8/100 → R = 100/8 = 12.5%. When money doubles at simple interest Rate = 100/Time. This relationship is a frequently tested shortcut in competitive exam problems about doubling or tripling periods.