A sum of money invested at simple interest becomes 17/10 of itself in 2 years and 6 months. What is the rate of interest per annum?

The final amount after 2 years and 6 months (or 2.5 years) is $$\frac{17}{10}$$​ of the principal.

Time = 2 years and 6 months = 2.5 years.

For simple interest, the relationship between the principal, interest, and amount is given by the formula:

​$$A = P \left( 1 + \frac{R \times T}{100} \right)$$​​

Where:

A is the final amount,

P is the principal,

R is the rate of interest per annum,

T is the time period in years.

Direct approach; 

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