The compound interest on Rs. 6250 at $8\%$  per annum for 1 year, compounded half yearly is

Principle P=Rs.6250,

rate of interest R= $\frac{8}{2}=4\%$ ($\because$ compounded half yearly)

 Time n=2($\because$ for one year two times compounded)

 C.I=?

$C.I=P{\left(1+\frac{R}{100}\right)}^n-P$

$C.I=6250{\left(1+\frac{4}{100}\right)}^2-6250$

$C.I=6250\times \frac{104}{100}\times \frac{104}{100}-6250$

$C.I=6760-6250=Rs.510$