Constant rates are used when two variables are in direct proportion. The cost to deliver 9 meals is $30
Given that:
[tex]\$10 \to 3\ meals[/tex]
[tex]\$16 \to 12\ meals[/tex]
Since the charging rate is constant, we do the following:
[tex]\$10 \to 3\ meals[/tex]
Multiply both sides by 3
[tex]\$10 \times 3 \to 3\ meals \times 3[/tex]
[tex]\$30 \to 9\ meals[/tex]
The above means that the cost to deliver 9 meals is $30
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