A sum of money becomes $$\frac {69}{50}$$​of itself in $$\frac{19}{5}$$​years when invested at simple interest. What is the rate of interest per annum?

Correct option is D

Given:
Principal (P) = Original sum of money
Amount (A) =$$\frac{69}{50} \times P$$​​
Time (T) =$$\frac{19}{5} years$$​​
Formula Used:
$$A = P + \text{SI}\\\text{SI} = \frac{P \times R \times T}{100}$$​​
Solution:
​$$\frac{69}{50} P = P + \frac{P \times R \times \frac {19}{5}}{100}\\\frac{69}{50} P - P = \frac{P \times R \times \frac {19}{5}}{100}\\\frac{19}{50} P = \frac{P \times R \times \frac {19}{5}}{100}\\R = \frac{19 \times 100}{50 \times \frac {19}{5}} = 10\%$$​​
Thus, the rate of interest per annum is 10%.