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6.03 Applications of scale factor to area, surface area and volume

Worksheet
Similar areas
1

The corresponding sides of two similar figures are in the ratio 7:3:

a

State the length scale factor from the left figure to the right figure.

b

State the area scale factor from the left figure to the right figure.

2

Consider the two given triangles on the Cartesian plane:

a

Find the scale factor used to enlarge the small triangle.

b

Find the scale factor used to reduce the large triangle.

c

Find the area of the small triangle.

d

Find the area of the large triangle.

e

Find the enlargement factor for the area of the small triangle.

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y
3

A triangle has side lengths of 7 \text{ cm}, 10 \text{ cm} and 16 \text{ cm}. A similar triangle has an area that is 9 times the area of the first triangle.

a

Find the length scale factor between the two triangles.

b

Find the side lengths of the second triangle.

c

Describe the relationship between the perimeters of the two triangles.

4

Find the value of x in each of the following:

a
b
c
5

If a square with an area of 25\text{ m}^{2} is dilated by a linear factor of 0.4, find the side length of the dilated square.

6

The corresponding sides of two similar triangles are 8 \text{ cm} and 40 \text{ cm}.

a

Find the length scale factor between the two triangles.

b

If the area of the smaller triangle is 24\text{ cm}^{2}, find the area of the larger triangle.

7

A square of side length 6 \text{ cm} is enlarged by a scale factor of 3. Find the area of the enlarged square.

8

The diameter of a circle is tripled. Describe what happens to its area.

9

Two pentagonal prisms are similar. The areas of their cross-sectional faces are given.

a

Calculate the surface area scale factor from Figure I to Figure II.

b

State the length scale factor from Figure I to Figure II.

c

Calculate the height of Figure II, if Figure I is 13 \text{ mm} high.

10

Consider the two similar rectangles shown below:

a

Find the area of rectangle A.

b

Find the area of rectangle B.

c

Determine the ratio of the area of rectangle A to rectangle B.

d

Hence, if the matching sides of two similar figures are in the ratio m:n, find the ratio of their corresponding areas.

11

Consider the formula A = \dfrac{1}{2} b h. If the values of both b and h are doubled, what effect would this have on the value of A?

12

Consider the formula A = \pi r^{2}.

a
If the value of r was tripled, what effect would this have on the value of A?
b
If r was divided by 4, what effect would this have on the value of A?
13

The cross-sectional areas of two similar rectangular prisms have dimensions: 6 \text{ cm} by 9 \text{ cm}, and 30 \text{ cm} by 45 \text{ cm} respectively.

a

Find the length scale factor.

b

Find the surface area scale factor.

c

Given that the surface area of the larger prism is 4425 \text{ cm}^{2}, find the surface area of the smaller prism.

14

Consider two similar parallelograms with matching sides in the ratio 6:8.

a

If the area of the smaller parallelogram is 72 \text{ cm}^{2}, calculate the area of the larger parallelogram.

b

Find the length of the base of the smaller parallelogram, if the length of the base of larger parallelogram is 12 \text{ cm}.

15

Two similar parallelograms have sides in the ratio 2:3. If the area of the larger parallelogram is 45 \text{ cm}^{2}, find the area of the smaller parallelogram.

Similar volumes
16

The volume of two similar crates are in the ratio 1331:125.

a

Find the ratio of their sides as an improper fraction.

b

Find the ratio of their surface areas as an improper fraction.

17

Consider the two similar trapezoidal prisms shown:

a

Find the length scale factor from the smaller prism to the larger prism.

b

Find the volume scale factor from the smaller prism to the larger prism.

18

Consider the following two rectangular prisms:

a

Are the two rectangular prisms similar?

b

Find the length scale factor.

c

Find the surface area scale factor.

d

Find the volume scale factor.

e

Find the volume scale factor, if the measurements of the smaller prism are doubled.

19

Two similar cones have circular bases with radii 7 \text{ cm} and 28 \text{ cm} respectively.

a

Find the scale factor of the height of the smaller cone to the height of the larger cone.

b

Find the scale factor of the volume of the smaller cone to the volume of the larger cone.

c

Find the volume of the larger cone, if the volume of the smaller cone is 852 \text{ cm}^{3}.

20

The following two solids are similar.

If the volume of the smaller solid is 193.7 \text{ cm}^{3} and the volume of the second is 24\,212.5 \text{ cm}^{3}, find the value of x.

21

The surface areas of two similar triangular prisms are in the ratio 64:49.

a

Find the ratio of their respective lengths.

b

Find the scale factor of their lengths.

c

Find the scale factor of their volumes.

22

Consider the two similar spheres shown. The smaller sphere has radius 3 \text{ cm} while the larger sphere has a radius of 12 \text{ cm}.

a

Find the volume of Sphere A, in exact form.

b

Find the volume of Sphere B, in exact form.

c

Find the ratio of the volume of Sphere A to Sphere B.

d

If the matching dimensions of two similar figures are in the ratio m:n, what ratio are their volumes in?

23

Two similar cylinders have volumes of 5760 \text{ cm}^{3}and 90 \text{ cm}^{3}:

a

Find the simplified ratio of the volume of the larger cylinder to the volume of the smaller cylinder.

b

Find the ratio of the height of the larger cylinder to the height of the smaller cylinder.

c

Hence, find the value of h.

Applications
24

The figure shows a rectangular field on which a game of tag is being played during a Physical Education class. To make it more of a fitness challenge, the teacher dilates the boundaries of the field by a factor of 1.5.

Find the area of the new field.

25

Consider two similar rectangular ceilings: the first with dimensions 5 \text{ m} by 4 \text{ m}, and the second with dimensions 20 \text{ m} by 16 \text{ m}.

a

Find the length enlargement factor.

b

Find the area enlargement factor.

c

The smaller ceiling took 1.5 \text{ L} of paint to cover it. How many litres of paint would be required to paint the larger ceiling?

26

A rectangular billboard has a length of 1.2 \text{ m}. The corresponding length on the designer's computer screen is 20 \text{ cm}.

a

Find the length enlargement factor.

b

Find the area enlargement factor.

c

Find the area of the computer screen image of the billboard, if the area of the actual board is 86.4 \text{ m}^{2}.

27

Susana has two teddy bears that have the same shape but are different sizes. The length of the first teddy bear is 15 \text{ cm}, while the length of the second teddy bear is 75 \text{ cm}.

a

Find the length enlargement factor.

b

Find the surface area enlargement factor.

c

If the smaller bear needs 375 \text{ cm}^{2} of fake fur to be covered, find the area of fake fur needed to cover the bigger bear.

28

The dimensions of a cement slab are the length, l, the width, w, and the thickness, h. If these dimensions are tripled, what will happen to:

a

The surface are of the cement slab.

b

The volume of the cement slab.

29

The radii of two spherical balloons are 12 \text{ cm} and 6 \text{ cm} respectively.

a

Write down a simplified ratio for the radii.

b

Find the ratio of their surface areas.

c

Find the ratio of their volumes.

d

Find the ratio of their volumes, if half the air is released from the smaller balloon.

30

Valentina was making a trial birthday cake for her son. The dimensions are 10 \text{ cm} for the length, 7 \text{ cm} for the width and 3 \text{ cm} for the height. The final cake needs to have dimensions of 20\text{ cm} for the length, 14 \text{ cm} for the width and 6 \text{ cm} for the height.

a

Find the ratio of the lengths of the final cake to those of the trial cake.

b

Hence, deduce the ratio of the volume of the final cake to that of the trial cake.

c

To make the final cake, what should Valentina multiply quantities of the trial cake by?

31

A beehive consists of hexagonal prisms each with side length of 3.2 \text{ mm} and depth of 3.8 \text{ mm}. A plastic container is built which is modelled on these hexagonal prisms, and has a side length of 6.4 \text{ cm}.

a

Find the ratio of the side length of the hexagonal prisms in the beehive to the side length of the plastic container.

b

Find the ratio of the surface area of the side of the hexagonal prisms in the beehive to the surface area of the side of the plastic container.

c

Find the ratio of the volume of the hexagonal prisms in the beehive to the volume of the modelled plastic container.

32

A model of the Eiffel tower is made with a height ratio of 1:6480.

a

Find the height of the model, in cm, if the height of the Eiffel tower is 324 \text{ m}.

b

Find the ratio of the surface area of the model to the surface area of the real Eiffel tower.

33

The ratio of the length of a model car to a real car is 1:20.

a

Find the ratio of the surface area of the model car to the surface area of the real car.

b

Find the ratio of the volume of the model car to the volume of the real car.

c

Find how many litres of paint are needed to paint the real car, if 18 \text{ mL} are needed to paint the model car.

d

Find the capacity of the model car fuel tank, in \text{mL}, if the real car fuel tank holds 48 \text{ L}.

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Outcomes

ACMGM024

obtain a scale factor and use it to solve scaling problems involving the calculation of the areas of similar figures

ACMGM025

obtain a scale factor and use it to solve scaling problems involving the calculation of surface areas and volumes of similar solids

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