In a direct proportional relationship, as one variable increases, the other variable increases at a constant rate. In this case, the cost \( y \) is directly proportional to the number of items purchased \( x \) at a rate of $1 per item.
The graph that represents this relationship would be a straight line that passes through the origin (0,0) with a slope of 1. This means that for every unit increase in \( x \) (number of items), \( y \) (cost) increases by 1.
To identify the correct graph:
- Look for a straight line.
- Ensure that the line passes through the origin (0, 0).
- Check that the slope of the line is 1 (for every increase of 1 in \( x \), \( y \) also increases by 1).
If you have specific graph options, please describe them, and I can help you identify which one correctly represents the proportional relationship.