To create the equation for the proportional relationship between the weight of the deli meat and its cost, we start with the information given:
- Nigel paid $10 for 2.5 pounds of roast beef.
Since the cost is proportional to the weight, we can express this relationship with the equation:
\[ y = kx \]
Where:
- \( y \) is the total cost,
- \( x \) is the weight in pounds,
- \( k \) is the constant of proportionality (price per pound).
To find \( k \), we can use the information provided:
\[ y = 10 \quad \text{(the cost)} \] \[ x = 2.5 \quad \text{(the weight)} \]
Now, substituting these values into the equation:
\[ 10 = k(2.5) \]
To solve for \( k \), divide both sides by 2.5:
\[ k = \frac{10}{2.5} = 4 \]
Now we can write the equation that represents the relationship:
\[ y = 4x \]
So, the equation for the graph of this proportional relationship is:
\[ y = 4x \]