Explanation:

- Each junior school student was charged Rs 325.

- Each senior school student was charged Rs 400.

- 80 students from the junior school participated.

- Combined average charged per student was Rs 352.

Let's calculate:

1. Total charge for 80 junior students:

80 * 325 = Rs 26,000.

2. Let the number of senior students be `x`.

Total charge for senior students = 400 * `x`.

3. Total students = 80 + `x`.

4. Total amount charged = 26,000 + 400 * `x`.

5. Average = $\frac{26,000+400x}{80+x}$.

6. Given average of Rs 352:

$$

\frac{{26,000 + 400x}}{{80 + x}} = 352

$$

Solve for `x`:

$$

26,000 + 400x = 352(80 + x)

$$

$$

26,000 + 400x = 28,160 + 352x

$$

$$

48x = 2,160

$$

$$

x = 45

$$

- Option 2: 45 is the correct answer.

.