Question

the graph represents the cost of a subscription to a newspaper.
weekly newspaper subscription
what is the constant of variation for the subscription cost based on the number of weeks?
$1.50
$7.50
$15.00
$30.00

Explanation:

Step1: Recall constant of variation formula

The constant of variation \( k \) for a direct variation \( y = kx \) is \( k=\frac{y}{x} \), where \( y \) is total cost and \( x \) is number of weeks.

Step2: Use a point to calculate \( k \)

Take the point \( (4, 30) \). Substitute \( x = 4 \) and \( y = 30 \) into \( k=\frac{y}{x} \).
\( k=\frac{30}{4}=7.50 \)
We can verify with another point, e.g., \( (8, 60) \): \( k=\frac{60}{8}=7.50 \), and \( (12, 90) \): \( k=\frac{90}{12}=7.50 \).

Answer:

\$7.50