​In how many years will a sum of money double itself at 6.25% per annum simple interest? ​

Correct option is A

Given:

6.25% 

Formula Used:

​$$SI = \frac{P \times R\times T}{ 100}$$​​

Solution:  

Let the principal = P 

after T time amount become = 2P 

Then, the interest = 2P - P = P 

Then, 

​$$P = \frac{P \times R\times T}{ 100}$$ 

P = $$\frac{ P \times 6.25 \times T}{100}$$ 

T = 16 years 

Alternative Solution:

6.25%  = 1 Year

6.25%$$\times$$2= 1$$\times$$2 years

12.50%$$\times$$​2=2$$\times$$2 Years

25%= 4Years

25%$$\times$$4= 4$$\times$$4Years

100% = 16 years

Option (a)