Question

1. A tool rental company charges $25 for the first hour of a tractor rental. Each additional hour costs $20 per hour. Which statement describes the relationship between total cost and hours?

A It is proportional; each ratio for related pairs is equivalent.
B It is proportional; each x-term is a multiple of the previous term.
C It is not proportional; each ratio y/x for related pairs is not equivalent.
D It is not proportional; each x-term is not a multiple of the previous term.​

Answer 1

C. It is not proportional. y/x ratios are not equivalent

Explanation:

Given a rental charge of $25 for the first hour and $20 for each additional hour, you want to know if the charges are proportional to the time.

Proportionality

In this situation, if the relationship were proportional, the charge per hour (constant of proportionality) would be the same for every hour. Here, the first hour costs more, so the hourly charge is not constant.

Here, we have, for x=hours, y=dollars, ...

(1, 25) ⇒ y/x = 25

(2, 45) ⇒ y/x = 22.5

(3, 65) ⇒ y/x ≈ 21.67

The y/x values are not constant (because the charge per hour is not constant). The relationship is not proportional.

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