The following is a stem and leaf plot of the scores of grade 9 students in an examination in Mathematics. How many students took the examination?

A letter or symbol that can represent different values is known as a variable.
A1. What do you call a letter or a symbol which can assume different values?
Answer: $\boxed{\text{Variable}}$

The data listed (Australian, American, Chinese, etc.) are categories or labels that describe attributes without numerical value or order.
A2. What category do the following data belong:
Answer: $\boxed{\text{Qualitative data (or Categorical data)}}$

When counting items like armchairs, books, or teachers, the data obtained are whole numbers that can be counted. This type of data is numerical and can only take specific, distinct values.
A3. What kind of data is derived when counting the number of arm chairs in a classroom, the number of books available and the number of teachers in a school?
Answer: $\boxed{\text{Quantitative discrete data}}$

To find the total number of students, count the number of leaves in the stem and leaf plot. Each leaf represents one student's score.

• Stem 9: 9 leaves (0, 0, 2, 3, 3, 4, 5, 6, 7)
• Stem 8: 10 leaves (1, 1, 2, 2, 4, 5, 8, 9, 9, 9)
• Stem 7: 7 leaves (2, 3, 4, 5, 6, 8, 9)
• Stem 6: 10 leaves (0, 1, 1, 1, 2, 3, 4, 7, 7, 8)

A4. How many students took the examination? Answer: $\boxed{\text{36 students}}$