Chaim is collecting aluminum cans for a recycling program. For every 10 bins that he fills
with cans, a local company donates $20 to his school. Chaim knows that this represents a
proportional relationship. He is writing a proposal to another company to ask for a matching
donation. In his proposal, Chaim needs to write the relationship in the form of an equation
and identify the constant of proportionality, or unit rate, that he earns. What equation should
he use, and what is the constant of proportionality? Explain how you found your answers.