HSC Mathematics Standard 2 Practice Exam

To determine how many students scored a perfect score of 100, we begin by calculating 20% of the total number of students.

Given that there are 30 students in total, we can express 20% as a fraction:

\[

20\% = \frac{20}{100} = 0.2

\]

Now, we multiply this percentage by the total number of students:

\[

0.2 \times 30 = 6

\]

Thus, 6 students scored a perfect score of 100.

This calculation shows that the correct answer is 6, but it's worth noting that 10 is the answer given by the student, which would represent 33.3% of the students instead of 20%, and does not match the conditions provided.