At what rate of interest (rounded off to two decimal places) per year will a sum of money double itself in 12 years on simple interest?

Correct option is B

Given:

A sum doubles in 12 years under simple interest SI.

Time, t = 12 years; Amount A = 2P.

Formula Used:

Simple Interest: $$\text{SI} = \dfrac{P \times r \times t}{100}$$​​

Amount: A = P + SI

Solution:
Since the sum doubles, A = 2P 

SI = A - P = P.
P =$$\frac{P \times r \times 12}{100}$$​​

1 = $$\frac{r \times 12}{100}$$​

r =$$\frac{100}{12} =$$​ 8.33%