We can solve this problem step-by-step:

1. Total number of students in the class = 40
2. Percentage of girls in the class = 60%

To find the number of girls: $\text{Number of girls} = 60\% \times 40 = \frac{60}{100} \times 40 = 24$

3. Percentage of girls who wear glasses = 25%

To find the number of girls who wear glasses: $\text{Number of girls who wear glasses} = 25\% \times 24 = \frac{25}{100} \times 24 = 6$

Therefore, 6 girls wear glasses.

Would you like more details on any part of the process?

Here are 5 related questions to explore:

1. If 75% of the boys wear glasses, how many boys wear glasses?
2. What percentage of the entire class wears glasses if 5 boys also wear glasses?
3. How many boys are in the class?
4. If 10% of the girls stop wearing glasses, how many girls would still wear glasses?
5. What is the ratio of girls wearing glasses to the total number of students in the class?

Tip: Always ensure percentages are calculated by converting them into fractions or decimals first!