Explanation:

- Let's denote the initial number of students as \( n \).

- The total initial weight is \( 58.5 \times n \) kg.

- Four new students join with a total weight of \( 49 + 51 + 54 + 68 = 222 \) kg.

- The new average weight becomes 58.3 kg with \( n + 4 \) students.

- The equation for the new total weight is:

$$

\frac{58.5n + 222}{n + 4} = 58.3

$$

- Solving for \( n \), we get:

$$

58.5n + 222 = 58.3(n + 4)

$$

$$

58.5n + 222 = 58.3n + 233.2

$$

$$

0.2n = 233.2 - 222

$$

$$

0.2n = 11.2

$$

$$

n = \frac{11.2}{0.2} = 56

$$

- The initial number of students was 56.

- Option 3: 56 is the correct answer .