Final answer:
The constant of proportionality in the given scenario is $0.85, which means that each bottle of sports drink costs $0.85.
Step-by-step explanation:
The question is asking to find the constant of proportionality, which represents the price per unit for an item, in this case, a sports drink. Given the prices listed ($0.85 for 1 bottle, $1.70 for 2 bottles, $2.55 for 3 bottles, and so on), it's clear that the price per bottle remains constant. Each example shows that the price is increasing directly in proportion to the number of bottles purchased.
To calculate the cost per bottle of the sports drink, we divide the total cost by the number of bottles. For the first example, the calculation would be $0.85 ÷ 1 bottle = $0.85 per bottle. Since every other example given doubles the initial amount for double the bottles, we know this pattern holds true for any number of bottles. Therefore, we can say with confidence that the constant of proportionality here is $0.85, meaning that each bottle of sports drink costs $0.85.