An amount becomes eight-fifth of the original amount in 5 years at what percentage rate of simple interest per annum?

Correct option is C

​Given:

Amount becomes $$\frac{8}{5} \times$$​ original amount in 5 years.

Formula Used:

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

$$\frac{\text{Amount}}{\text{Principal}} = 1 + \frac{R \times T}{100}$$​​

Solution: 

Applying the formula :

​$$\frac{8}{5} = 1 + \frac{R \times 5}{100}$$​​

$$\frac{8}{5} - 1 = \frac{5R}{100}$$​​

$$\frac{3}{5} = \frac{5R}{100}$$​​

$$R = \frac{3 \times 100}{5 \times 5} = 12\%$$​​