Given:
- Principal amount (P) = Rs 5000
- Amount (A) = Rs 7520
- Time (T) = 3 years

To find:
- Rate of interest (R)

Solution:

Step 1: Calculate the simple interest (S.I.) using the formula:
S.I. = (P * R * T) / 100

Step 2: Substitute the given values in the formula:
S.I. = (5000 * R * 3) / 100

Step 3: Simplify the equation:
S.I. = 15000R / 100
S.I. = 150R

Step 4: Calculate the amount (A) using the formula:
A = P + S.I.
7520 = 5000 + 150R

Step 5: Simplify the equation:
2520 = 150R

Step 6: Solve for R:
R = 2520 / 150
R = 16.8

Therefore, the rate of interest is 16.8% per annum.

Explanation:

- The formula to calculate simple interest is S.I. = (P * R * T) / 100, where P is the principal amount, R is the rate of interest, and T is the time in years.
- In this question, we are given the principal amount (P) as Rs 5000, the amount (A) as Rs 7520, and the time (T) as 3 years.
- We need to find the rate of interest (R).
- By substituting the given values in the formula, we get the equation S.I. = (5000 * R * 3) / 100.
- Simplifying the equation, we get S.I. = 15000R / 100, which can be further simplified to S.I. = 150R.
- We know that the amount (A) is equal to the principal amount plus the simple interest, so we can write the equation as 7520 = 5000 + 150R.
- Simplifying this equation, we get 2520 = 150R.
- Solving for R, we find that the rate of interest is 16.8% per annum.