Title: Lesson 6-4
Author: mark_cameron
Last saved by: gtsmith
Company: McGraw-Hill

Lesson 6-7

Example 1 Write an Equation for a Function
Input, x | 1 | 2 | 3 | 4 | 5
Output, y | 6 | 12 | 18 | 24 | 30
Write an equation to represent the function displayed in the table. 

Examine how the value of each input and output changes.
Input, x | Multiply by 6 | Output, y

1
2
3
4
5

1 × 6
2 × 6
3 × 6
4 × 6
5 × 6

6
12
18
24
30

Each output y is equal to 6 times the input x. So, the equation that represents the function is y = 6x. 

Example 2 Real-World Example
MONEY Aidan mows lawns each summer. He charges $15 for each lawn he mows.
Make a table to show the relationship between the number of lawns mowed ℓ and the total amount earned t.

The total earned (output) is equal to $15 times the number of lawns mowed (input).

Lawns 
Mowed, ℓ

Multiply 
by 15

Total 
Earned ($), t

1
2
3
4

1 × 15
2 × 15
3 × 15
4 × 15

15
30
45
60

Example 3 Real-World Example
MONEY Aidan mows lawns each summer. He charges $15 for each lawn he mows.
Write an equation to find the total amount earned t for mowing ℓ lawns.

Study the table from Example 2. The total earned equals $15 times the number of lawns mowed.

Words

Variable

Equation

Total earned equals $15 times the number of lawns mowed.

Let t represent the total earned and 
ℓ represent the number of lawns mowed.

t     =     15     ∙     ℓ

So, the equation is t = 15ℓ.

Example 4 Real-World Example
MONEY Aidan mows lawns each summer. He charges $15 for each lawn he mows.
How much will Aidan earn if he mows 20 lawns?

t = 15ℓ	Write the equation.
t = 15 ∙ 20	Replace ℓ with 20.
t = 300	Multiply.

Aidan will earn $300 for mowing 20 lawns.

Example 5 Real-World Example

Number of People, p

Total 
Cost ($), t

1 | 8
2 | 16
3 | 24
4 | 32
POOLS The cost of admission at a public pool is shown in the table. Write a sentence and an equation to describe the data. Then find the total cost of admission for a group of 7 friends.

The cost of admission is $8 for each person. 
The total cost t is $8 times the number of people p. Therefore, t = 8p. Use this equation to find the total cost t of admission for 7 people.

t = 8p	Write the equation.
t = 8 ∙ 7 or 56	Replace p with 7. Multiply.

The total cost of admission for 7 people is $56.