If the compound interest on a sum for 2 years at 12 1\2% per annum is Rs. 510, the simple interest on the same sum at the same rate for the same period of time is :

Explanation:

Rate %= 12 1\2%=1\8=9→Amt.\8→Pri.

According to the question,

17 units = Rs. 510

1 unit = Rs. 30

64 units = Rs. 30×64= Rs. 1920

Hence principal = R5. 1920

SI for 2 years

= 12 1\2×2=25 %

Required SI = 1920×25\100=Rs.480

Hence, Required SI = Rs.480