notes over 4.5 writing a direct variation equation in exercises 1-6, the variable x and y vary...

k

Notes Over 4.5Writing a Direct Variation EquationWriting a Direct Variation Equation

In Exercises 1-6, the variable x and y vary directly. Use the given values to write an equation that relates x and y.

y kx

k

15 5

Direct Variation

Two quantities that model the equation y = kx, where k is the constant of variation

x x

y

x

1 3 15. , x y

3

y 5x

k



y kx

k

3 1

2

Direct Variation


x x

y

x

2 6 3. , x y

6

y 1

2x

k



y kx

k

4 1

Direct Variation


x x

y

x

3 4 4. , x y

4

y x

k



y kx

k

2 1

5

Direct Variation


x x

y

x

4 10 2. , x y

10

y 1

5x

k



y kx

k

7 2

Direct Variation


x x

y

x

5 35 7. . , x y

35.

y 2x

k



y kx

k

4 1

3

Direct Variation


x x

y

x

6 12 4. , x y

12

y 1

3x

Notes Over 4.5Using a Ratio to Write a ModelUsing a Ratio to Write a Model

E M150

57120

150

57

5M

The person’s weight on Mars would be pounds. 45

3

5

7. Use the ratio model to estimate a

person’s weight on Mars if the person weighs 120

pounds on Earth.

E M150

57

150

57

228

5

4


E M150

5762

9300

57The person’s weight on Earth would

be 163.2 pounds.

8. Use the ratio model to estimate a

person’s weight on Earth if the person weighs 62

pounds on Mars.

E M150

57

E


E V160

139

9. A person who weighs 160 pounds on Earth weighs 139 pounds on Venus.

a. Write a model that relates a person’s weight E on Earth to that person’s weight V on Venus.

E kV

k

V V

E

V160139


E V160

139

9. A person who weighs 160 pounds on Earth weighs 139 pounds on Venus.

b. A person weighs 195 pounds on Earth. Use the model to estimate that person’s weight on Venus.

160

139 160

139195

32

39

V5421

32The person’s weight on Venus would be

169.4 pounds.

Notes Over 4.5

notes over 4.5 writing a direct variation equation in exercises 1-6, the variable x and y vary...

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