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 \( y = kx \) (where \( y \) is total cost and \( x \) is number of weeks) is \( k=\frac{y}{x} \).

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

Take the point \((4, 30)\). Substitute \( x = 4 \) and \( y = 30 \) into \( k=\frac{y}{x} \).
\( k=\frac{30}{4}=7.5 \).
We can verify with another point, e.g., \((8, 60)\): \( k=\frac{60}{8}=7.5 \), or \((12, 90)\): \( k=\frac{90}{12}=7.5 \).

Answer:

\$7.50