Explanation:

To find the sum where the difference between compound interest (CI) and simple interest (SI) over 2 years is Rs 80 at an interest rate of 20% per annum, we can follow these points:

- Simple Interest (SI) Formula: SI = (Principal × Rate × Time) / 100

- Compound Interest (CI) after 2 years Formula:

- CI = Principal × (1 + Rate/100)^Time - Principal

- Given: Difference between CI and SI for 2 years = Rs 80

The formula for the difference when CI and SI are given over 2 years is:

- Difference = Principal × (Rate/100)^2

Now, solve for the Principal (P) using:

- 80 = P × (20/100)^2

- 80 = P × 0.04

- P = 80 / 0.04 = Rs 2,000

- Option: 1, Rs 1,200

- Incorrect, calculation doesn't match the difference.

- Option: 2, Rs 2,000

- Matches the calculated Principal.

- Option: 3, Rs 1,500

- Incorrect, doesn't satisfy the condition.

- Option: 4, Rs 1,000

- Incorrect, too low for the difference given.

?? Your Correct Answer: Option: 2, Rs 2,000