At what rate of interest (in percentage) per year will a sum of money double itself in 5 years on simple interest?

Correct option is B

Given:

Time T = 5 years

Amount doubles on Simple Interest

Final amount = 2P 

Interest earned = P

Formula Used:

Simple Interest: $$\text{SI} = \dfrac{P \times R \times T}{100}$$​​

Solution:
Since SI = P,
P$$=\frac{P \times R \times 5}{100}$$​​

1$$=\frac{R \times 5}{100}$$​

R=$$\frac{100}{5}=$$​20%.