If a certain sum of money becomes thrice of itself in 7 years 3 months at simple interest, then what will be the annual rate of interest?

A sum of money becomes thrice of itself in 7 years 3 months (7.25  year) under simple interest.

In simple interest, if a principal P becomes n times of itself in a given period T,

then the interest SI is (n−1)P. Here, since the sum triples, n = 3 and SI = 2P

​$$\text{Simple Interest (SI)} = \frac{P \times R \times T}{100}$$​​

$$2P = \frac{P \times R \times 7.25}{100}\\ \ \\R= \frac{2\times200}{7.25}\\ \ \\ R= \frac{200}{7.25}\\ \ \\ R = 27.58\%$$ 

Thus, correct option is (d).