Question

A small grocery store offers two different brands of milk.

Brand A 2% milk costs $3.50 a gallon.
Brand B whole organic milk costs $3.00 for a half-gallon plus a one-time deposit of $1.50 for the glass jug. Once the glass jug deposit has been paid, the jug can be brought back to the store and the deposit doesn't have to be paid for each additional half-gallon milk that is purchased.
Graph the cost of milk for the brand that is proportional.

Answer 1

The proportional brand is Brand A (cost is $3.50 per gallon). Its cost is directly proportional to the number of gallons.

Equation: C = 3.50g, where g = gallons and C = cost in dollars.

To graph:
- Horizontal axis: gallons (g). Vertical axis: cost in dollars (C).
- Plot points (g, C): (0, 0), (1, 3.50), (2, 7.00), (3, 10.50), ...
- Draw a straight line through those points (passes through the origin) with slope 3.50.

(Brand B is not proportional because of the $1.50 one-time jug deposit, which makes the line have a nonzero intercept.)