Which of the following variables is not continuous?

• A. The number of cars passing through an intersection in an hour
• B. The amount of rainfall measured in $\mathrm{mm}$
• C. The height of students in a classroom (in $\mathrm{cm}$)
• D. The time taken to run a marathon (in $\mathrm{hours}$)

Answer: (A)

Verified step by step guidance

1. Understand the difference between continuous and discrete variables. Continuous variables can take any value within a range, including fractions and decimals, while discrete variables take countable, distinct values, often integers.
2. Examine each variable given: 'The amount of rainfall measured in millimeters' can be any value, including decimals, so it is continuous.
3. 'The height of students in a classroom (in centimeters)' can also take any value within a range and is measured with precision, so it is continuous.
4. 'The time taken to run a marathon (in hours)' can be measured very precisely, including fractions of hours, so it is continuous.
5. 'The number of cars passing through an intersection in an hour' counts whole cars, which cannot be divided into fractions, so it is a discrete variable and therefore not continuous.