Explanation:

Let's assume the Principal = 100

S.I for 2 years as per the given parameters = 100*10% = 10

C.I for 2 years with the same parameters = 100*10.25% = 10.25

=> 10 ------------------> 50 Rs.

       1 ------------------> 50/10 = 5 Rs.    

10.25 ------------------> 5*10.25 = 51.25 Rs.