Question

Cortez's workout plan involves a total of 65 minutes of running and swimming. He burns 15 calories per minute when running and 6 calories per minute when swimming. Let r represent the amount of time he spends running. Write an expression to represent the amount of calories that he burns.

Answer 1

`E=9r+390`

Step-by-step explanation:

Function Modeling

We can express the relations between different variables and magnitudes in mathematics formulas. This allows us to better manipulate the field data and even make predictions and take decisions out of them.

We know Cortez spends a total of 65 minutes of running and swimming. Let's call r the minutes of running and s the minutes of swimming. The first condition implies that

`r+s=65`

Or, equivalently

`s=65-r`

The energy burnt when running are 15 calories per minute. It means that he burns 15r in r minutes. Similarly, Cortez burns 6s calories when swimming. The total energy he burns is

`E=15r+6s`

Replacing the formula for s, we get

`E=15r+6(65-r)`

`\boxed{E=9r+390}`

That formula gives the total calories Cortez burns in r minutes of running