Scale Factors

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Scale Factors and Volume

Discovering the effect on the volume of a prism when its dimensions are multiplied by a scale factor

Find the volume of each prism 2.

1.

15cm 24m 14m

38cm

9cm

11m

V  1,848m

3

V  5,130cm

3

Objective •

Given a prism with its dimensions multiplied by a scale factor, you will find the NEW volume without using a formula.

Purpose •



• •

Architects need to know the effect of scale factors on volume when they make scale models of buildings. Gardeners need to know the effect of scale factors on volume when doubling the dimensions of a flowerbed in order to purchase the correct amount of soil. Knowing the effect of scale factors on volume is a 7th grade standard. There is one item on the CAHSEE related to scale factors and volume.

Suppose the length, width, and height of this container were doubled.

We call this “multiplying by a scale factor of 2.”

Suppose the length, width, and height of this container were tripled.

We call this “multiplying by a scale factor of 3.”

What is a scale factor? •



In your own words, give a description of a scale factor. Share your description with your partner.

How many cubes do you believe would fill this container if the length, width, and height were doubled?

Let’s Explore… We know that the volume of a 40 foot container is 2,752 ft3. What do you suppose would happen to the volume if we multiplied the length, width and height by a scale factor of 2? Or by a scale factor of 3? Or by a scale factor of 4?

First, let’s make a table

Original

x2 x3 x4

x5

Length

Width

Height

Volume

Volume compared to original

40

8

8.6

2,752 ft3

SAME

We will multiply our original dimensions by a scale factor of 2 and complete our table.

h 2

l 2

w 2

l  40 l  2  40  2  80

Let’s complete our table

Original

x2 x3 x4

x5

Length

Width

Height

Volume

Volume compared to original

40

8

8.6

2,752 ft3

SAME

80

We will multiply our original dimensions by a scale factor of 2 and complete our table.

h 2

l 2

w 2

w8 w  2  8  2  16

Let’s complete our table Length

Width

Height

Volume

Volume compared to original

Original

40

8

8.6

2,752 ft3

SAME

x2

80

16

x3 x4

x5

We will multiply our original dimensions by a scale factor of 2 and complete our table.

h 2

l 2

w 2

h  8.6 h  2  8.6  2  17.2

Let’s complete our table Length

Width

Height

Volume

Volume compared to original

Original

40

8

8.6

2,752 ft3

SAME

x2

80

16

17.2

x3 x4

x5

Let’s complete our table Length

Width

Height

Volume

Volume compared to original

Original

40

8

8.6

2,752 ft3

SAME

x2

80

16

17.2

22,016

x3

Find the volume V=(80)(16)(17.2) V=22,016

x4

x5

Let’s complete our table Length

Width

Height

Volume

Volume compared to original

Original

40

8

8.6

2,752 ft3

SAME

x2

80

16

17.2

22,016 ft3

23 or 8 times larger

x3 x4

x5

Maybe you should22,016 It2,752 got divide. bigger! 3 8 or 2 What

happened??



Now, we will multiply our original dimensions by a scale factor of 3 and complete our table.

h3

l 3

w 3

l  40 l  3  40 40  3  120

Let’s complete our table Length

Width

Height

Volume

Volume compared to original

Original

40

8

8.6

2,752 ft3

SAME

x2

80

16

17.2

22,016 ft3

23 or 8 times larger

x3

120

x4

x5

Now, we will multiply our original dimensions by a scale factor of 3 and complete our table.

h3

l 3

w 3

w8 w  3  8  3  24

Let’s complete our table Length

Width

Height

Volume

Volume compared to original

Original

40

8

8.6

2,752 ft3

SAME

x2

80

16

17.2

22,016 ft3

23 or 8 times larger

x3

120

24

x4

x5

Now, we will multiply our original dimensions by a scale factor of 3 and complete our table.

h3

l 3

w 3

h  8.6 h  3  8.6  3  25.8

Let’s complete our table Length

Width

Height

Volume

Volume compared to original

Original

40

8

8.6

2,752 ft3

SAME

x2

80

16

17.2

22,016 ft3

23 or 8 times larger

x3

120

24

25.8

x4

x5

Let’s complete our table Length

Width

Height

Volume

Volume compared to original

Original

40

8

8.6

2,752 ft3

SAME

x2

80

16

17.2

22,016 ft3

23 or 8 times larger

x3

120

24

25.8

74,304

x4

x5

Find the volume V=(120)(24)(25.8) V=74,304

Let’s complete our table Length

Width

Height

Volume

Volume compared to original

Original

40

8

8.6

2,752 ft3

SAME

x2

80

16

17.2

22,016 ft3

23 or 8 times larger

x3 x4

x5

120

24

Need help?

25.8

Didn’t I 3 74,304 fttell 33 or 27 times you already? larger

74,304  2,752  What

3 27 or 3 happened??

Let’s complete our table Length

Do you see a Width Height pattern? Try completing the next row 8.6 on8your own.

Volume

Volume compared to original

2,752 ft3

SAME

Original

40

x2

80

16

17.2

22,016 ft3

23 or 8 times larger

x3

120

24

25.8

74,304 ft3

33 or 27 times larger

x4

x5

Let’s complete our table What canyou Maybe Length Width Height you should conclude? complete the last row.

Volume

Volume compared to original

Original

40

8

8.6

2,752 ft3

SAME

x2

80

16

17.2

22,016 ft3

23 or 8 times larger

x3

120

24

25.8

74,304 ft3

33 or 27 times larger

x4

160

32

34.4

176,128 ft3

43 or 64 times larger

x5

Let’s complete our table Length

Last clue. Width Height What do you notice about these two 8 8.6 columns?

Volume

Volume compared to original

2,752 ft3

SAME

Original

40

x2

80

16

17.2

22,016 ft3

23 or 8 times larger

x3

120

24

25.8

74,304 ft3

33 or 27 times larger

x4

160

32

34.4

176,128 ft3

43 or 64 times larger

x5

200

40

43

344,000 ft3

53 or 125 times larger

True or False? •

Whenever the length, width, and height are multiplied by a scale factor of 2, the original volume is multiplied by 23? or True

False

True or False? •

Whenever the length, width, and height are multiplied by a scale factor of 3, the original volume is multiplied by 34? or True

False

True or False? •

Whenever the length, width, and height are multiplied by a scale factor of 23, the original volume is multiplied by 232? or True

False

True or False? •

Whenever the length, width, and height are multiplied by a scale factor of 54, the original volume is multiplied by 543? or True

False

True or False? •

Whenever the length, width, and height are multiplied by a scale factor of x, the original volume is multiplied by x 3? or True

False

Let’s take a look at triangular prisms…

Will the same pattern work with triangular prisms?

5 ft

5 ft 4 ft

6 ft

14 ft

First, let’s make a table

Original

x2 x3 x4

x5

Base of the triangle

Height of the triangle

Height of the prism

Volume

Volume compared to original

6

4

14

168 ft3

SAME

We will multiply our original dimensions by a scale factor of 2 and complete our table.

2

5 ft

5 ft 4 ft

6 ft 2

14 ft

2

Let’s complete our table

Original

x2 x3 x4

x5

Base of the triangle

Height of the triangle

Height of the prism

Volume

Volume compared to original

6

4

14

168 ft3

SAME

12

8

28

Let’s complete our table Base of the triangle

Height of the triangle

Height of the prism

Volume

Volume compared to original

Original

6

4

14

168 ft3

SAME

x2

12

8

28

1,344

x3

Find the volume Area of the base = ½(12)(8) x4 Area of the base = 48 V=(48)(28) x5 V=1,344

Let’s complete our table Base of the triangle

Height of the triangle

Height of the prism

Volume

Volume compared to original

Original

6

4

14

168 ft3

SAME

x2

12

8

28

1,344 ft3

23 or 8 times larger

x3 x4

x5

Make sure you check your work!

Don’t ask me!  1,344  168

What happened?? 8 or

23

We will multiply our original dimensions by a scale factor of 3 and complete our table.

3

5 ft

5 ft 4 ft

6 ft 3

14 ft

3

Let’s complete our table Base of the triangle

Height of the triangle

Height of the prism

Volume

Volume compared to original

Original

6

4

14

168 ft3

SAME

x2

12

8

28

1,344 ft3

23 or 8 times larger

x3

18

12

x4

x5

42

Let’s complete our table Base of the triangle

Height of the triangle

Height of the prism

Volume

Volume compared to original

Original

6

4

14

168 ft3

SAME

x2

12

8

28

1,344 ft3

23 or 8 times larger

x3

18

12

42

4,536

Find the volume Area of the base = ½(18)(12) Area of the base = 108 x5 V=(108)(42) V=4,536 x4

Let’s complete our table Base of the triangle

Height of the triangle

Height of the prism

Volume

Volume compared to original

Original

6

4

14

168 ft3

SAME

x2

12

8

28

1,344 ft3

23 or 8 times larger

42

Sorry, I can’t or 27 times 4,536give ft3 you33any more help.larger

x3 x4

x5

18

12

4,536  168 

What happened?? 27 or

33

Let’s complete our table By George, I you’veHeight Base ofthink Height Keepof the the gotofit!the going! prism triangle triangle

Volume

Volume compared to original

Original

6

4

14

168 ft3

SAME

x2

12

8

28

1,344 ft3

23 or 8 times larger

x3

18

12

42

4,536 ft3

33 or 27 times larger

x4

x5

Let’s complete our table Go ahead and Basecomplete of Heightthe Height the lastofrow. the of the

Volume

Volume compared to original

triangle

triangle

prism

Original

6

4

14

168 ft3

SAME

x2

12

8

28

1,344 ft3

23 or 8 times larger

x3

18

12

42

4,536 ft3

33 or 27 times larger

x4

24

16

56

10,752 ft3

43 or 64 times larger

x5

Let’s complete our table Did it work?

Base ofCanHeight we say Height the that ofthis the of the triangle triangle pattern is true prism

Volume

Volume compared to original

Original

6 for all prisms? 4 14

168 ft3

SAME

x2

12

8

28

1,344 ft3

23 or 8 times larger

x3

18

12

42

4,536 ft3

33 or 27 times larger

x4

24

16

56

10,752 ft3

43 or 64 times larger

x5

30

20

70

21,000 ft3

53 or 125 times larger

True or False? •

The volume of a triangular prism is 100m3. If the dimensions are multiplied by a scale factor of 2, the new volume will be 800m3.

or True

False

True or False? •

The volume of a triangular prism is 310 ft3. If the dimensions are multiplied by a scale factor of 2, the new volume will be 620 ft3.

or True

False

True or False? •

The volume of a rectangular prism is 10 km3. If the dimensions are multiplied by a scale factor of 4, the new volume will be 270 km3.

or True

False

True or False? •

The volume of a rectangular prism is 21 yd3. If the dimensions are multiplied by a scale factor of 3, the new volume will be 567 yd3. or True

False

True or False? •

The volume of a rectangular prism is 50 m3. If the dimensions are multiplied by a scale factor of x, the new volume will be 50x3 m3. or True

False

On your own… •

1,080 ft3 •

54 cm3 •

3

Suppose the volume of a rectangular prism is 40 ft3. Find the new volume, if the dimensions are multiplied by a scale factor of 3. Suppose the dimensions of a triangular prism are multiplied by a scale factor of 2 and the NEW volume is 432 cm3, what was the original volume? Suppose the original volume of a triangular prism is 120 m3 and the NEW volume is 3,240 m3, what scale factor were the dimensions multiplied by?

Let’s wrap it up! Give a brief explanation of what would happen to the volume of the following prism if the dimensions were multiplied by a scale factor.

19ft

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