The C.I. on a certain sum for 2 years at 10% per annum is Rs. 525. The S.I. on the same sum for double the time at half the rate percent per annum is________?

A. Rs. 400
B. Rs. 500
C. Rs. 600
D. Rs. 800
Explanation:
Let the sum be Rs. P. Then,
[P(1 + 10/100)2 – p] = 525
P[(11/10)2 – 1] = 525
P = (525 * 100) / 21 = 2500
Sum = Rs. 2500
So, S.I. = (2500 * 5 * 4)/100 = Rs. 500