Let the sum be Rs. 100. Then,
S.I. for first 6 months = Rs.[ (100 x 10 x 1)/(100 x 2) ]= Rs.5
S.I. for last 6 months =Rs.[(102 x 10 x 1)/(100 x 2) ] = Rs.5.25
So, amount at the end of 1 year = Rs. (100 + 5 + 5.25) = Rs. 110.25
Effective rate = (110.25 - 100) = 10.25%