6th Grade Math Textbook, Fundamentals

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13-5

The constant difference is 20.

 20

 20

 20

 20

The constant difference is 45.

 45

 45

 45

 45

Manny earns $45 an hour tutoring. For each tutoring session, he donates

$5 to charity and saves the remaining amount. Write a function rule to

describe the relationship between the number of hours per session and

the amount he saves. Create a function table to help see the relationship.

Let xthe number of hours per tutoring session.

Let ythe amount Manny saves.

Write the function rule as y 45 x5.

Length of Session

(hours)

Amount Saved

(dollars)

1 45  5  40

2 90  5  85

3 135  5  130

4180  5  175

5 225  5  220

Functions

Objective To write a function rule to represent a situation• To evaluate a function given a

specific domain• To evaluate a function when the domain is not specified

A jet airplane climbs 20 feet in altitude for each second after

takeoff. Write an equation, or a function rule, that describes

the relationship between elapsed time and the altitude.

To write a function rule, first define the variables. Then write

a function rule comparing the relationship between time

and altitude.

Create a to help see the relationship.

A function table helps organize and display the x- and

y-values of a function.

Let xtime in seconds.

Let yaltitude in feet.

Write the function rule as y 20 x.

xy

120

240

360

480

5100

function table

1