A table of x- and y-values is shown.

Question

X, Y
3|12
5|20
7|28
What is the constant of proportionality that relates y to x
A. 1/4
B. 4
C. 1/8
D. 8

Answer 1

To find the constant of proportionality that relates $y$ to $x$, we can use the formula for proportionality, which states that $y=kx$ where $k$ is the constant of proportionality.

We can calculate $k$ for each pair of $(x,y)$ values provided in the table:

1. For $(3,12)$: $$k=\frac{y}{x}=\frac{12}{3}=4$$

2. For $(5,20)$: $$k=\frac{y}{x}=\frac{20}{5}=4$$

3. For $(7,28)$: $$k=\frac{y}{x}=\frac{28}{7}=4$$

In all cases, the constant of proportionality $k$ is 4.

Therefore, the answer is $\text{B. }4$.