What is the compound interest on the sum of ₹15625 for 2 years at the rate of 12% per annum, if the interest is 8 months is compounded ?

Given, 

Principal (P) = ₹15625

Rate (r) = 12% $$\longrightarrow\ $$ $$12\times\ \frac{8}{12}=8\%$$ (compounded 8 monthly) 

Time = 2 year $$\longrightarrow\ $$ $$2\times\ \frac{12}{8}=3$$

As we know, 

CI = $$P\left(\left(1+\frac{r}{100}\right)^t-1\right)$$

= $$15625\left(\left(1+\frac{8}{100}\right)^3-1\right)$$

= $$15625\left(\left(\frac{27}{25}\right)^3-1\right)$$

= $$15625\left(\frac{19683}{15625}-1\right)$$

= ₹4058

Hence, Option B is correct.