IM: 8.5.3: Equations for Functions (Lesson)

Write an algebraic expression for the rule in the box in the diagram.

Record your answers to these questions in the table provided.

1. Match each of these descriptions with a diagram:

a. the circumference, C, of a circle with radius, r b. the distance in miles, d, that you would travel in t hours if you drive at 60 miles per hour c. the output when you triple the input and subtract 4 d. the volume of a cube, v given its edge length, s

2. Write an equation for each description that expresses the output as a function of the input.

3. Find the output when the input is 5 for each equation.

4. Name the independent and dependent variables of each equation.

Choose a 3-digit number as an input.

Apply the following rule to it, one step at a time:

• Multiply your number by 7.

• Add one to the result.

• Multiply the result by 11.

• Subtract 5 from the result.

• Multiply the result by 13

• Subtract 78 from the result to get the output.

Can you describe a simpler way to describe this rule? Why does this work?

If Jada has 30 dimes, how many quarters does she have?

Is the number of quarters a function of the number of dimes? If yes, write a rule (that starts with q =...) that you can use to determine the output, q, from a given input, d. If no, explain why not.