1.  The compound interest on a certain sum for 2 years at 10% per annum is ₹ 525. The simple interest on the same sum for double the time at half the rate percent per annum is:
A. ₹ 400
B. ₹ 500
C. ₹ 600
D. ₹ 800

Answer: Option B

Explanation:

Let the sum be ₹ P.

Then, P 1 + 10 2 - P = 525
100

⇒ P 11 2 - 1 = 525
10

⇒ P = 525 x 100 = 2500.
21

∴ Sum = ₹ 2500.

So, S.I. = ₹ 2500 x 5 x 4 = ₹ 500
100