A proportional relationship between two variables can be express as:
Let's write the relationships given so we can determine which is proportional.
The circumference and a diameter are related by:
The area and the length of a side of a square are related by:
The perimeter and the width of a rectangle are related by the equation:
The Fahrenheit and Celsius are related by:
By looking at all the expression we notice that onle the first one is a proportional relationship.
Therefore, the circumference and diameter of a circle