Question

roxanne is measuring the diameter and the radius of different - sized circles. there is a proportional relationship between the radius of the circle in inches, x, and the diameter of the circle in inches, y. what is the constant of proportionality? write your answer as a whole number or decimal. inches in diameter per inch in radius

unit rates
not feeling ready yet? these can help: work it out
lesson: proportional relationships

Explanation:

Step1: Recall proportion formula

The relationship between diameter $y$ and radius $x$ is $y = kx$, where $k$ is the constant of proportionality.

Step2: Calculate $k$ using a data - pair

Take any pair from the table, say $x = 10$ and $y=20$. Substitute into $y = kx$, we get $20=k\times10$. Solving for $k$ gives $k = \frac{y}{x}=\frac{20}{10}=2$.

Answer:

2