Explanation:

- There are 50 students in the class.

- 40% of 50 students are girls, so there are 20 girls and 30 boys.

- Average weight of boys is 62 kg.

- Average weight of girls is 58 kg.

- To find the average weight of the whole class:

$$

\text{Total weight of all students} = (30 \times 62) + (20 \times 58)

$$

$$

= 1860 + 1160 = 3020 \text{ kg}

$$

$$

\text{Average weight of the whole class} = \frac{3020}{50} = 60.4 \text{ kg}

$$

- Option 1: 60.4 kg is the correct average weight.

Option 1: 60.4 is correct.