Mathematics
Grade 6
15 min
Similar solids
Similar solids
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1
Introduction & Learning Objectives
Learning Objectives
Identify similar three-dimensional solids.
Define and calculate the scale factor between two similar solids.
Use the scale factor to find missing linear dimensions of similar solids.
Understand and apply the relationship between the scale factor and the ratio of surface areas of similar solids.
Understand and apply the relationship between the scale factor and the ratio of volumes of similar solids.
Solve real-world problems involving similar solids, including finding unknown surface areas or volumes.
Have you ever seen a miniature model of a car or a building? 🚗🏢 How is that small model related to the real, much larger object?
In this lesson, we'll explore 'similar solids' – three-dimensional shapes that look exactly alike but are diffe...
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Key Concepts & Vocabulary
TermDefinitionExample
Solid (3D Shape)A three-dimensional object that has length, width, and height, occupying space. Examples include cubes, spheres, and pyramids.A shoebox is a rectangular prism, which is a solid shape.
Similar ShapesTwo-dimensional figures that have the same shape but different sizes. All corresponding angles are equal, and corresponding sides are proportional.A small square and a large square are similar shapes.
Similar SolidsThree-dimensional objects that have the exact same shape but different sizes. Their corresponding linear dimensions (like edges, heights, or radii) are all proportional.A small basketball and a larger basketball are similar solids.
Corresponding PartsParts (such as edges, faces, heights, or radii) that are in the same relative position in two or...
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Core Formulas
Ratio of Linear Dimensions (Scale Factor)
$k = \frac{\text{Linear Dimension of Solid 2}}{\text{Linear Dimension of Solid 1}}$
To find the scale factor (k) between two similar solids, divide any linear dimension of the second solid by the corresponding linear dimension of the first solid. This ratio will be constant for all corresponding lengths.
Ratio of Surface Areas
$\frac{\text{Surface Area}_2}{\text{Surface Area}_1} = k^2$
If the scale factor between two similar solids is 'k', then the ratio of their surface areas is the square of the scale factor ($k^2$). Use this to find a missing surface area or the ratio of areas.
Ratio of Volumes
$\frac{\text{Volume}_2}{\text{Volume}_1} = k^3$
If the scale factor between two similar solids is 'k', then th...
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Challenging
A company sells juice in two similar cylindrical bottles. The 'Regular' bottle is 12 cm tall and holds 400 mL. The 'Jumbo' bottle is 18 cm tall. How much juice does the 'Jumbo' bottle hold? (Note: 1 mL = 1 cm³)
A.600 mL
B.800 mL
C.900 mL
D.1350 mL
Challenging
A large cube is perfectly built from 125 smaller, identical cubes. If the total surface area of one small cube is 6 cm², what is the total surface area of the large cube?
A.30 cm²
B.150 cm²
C.375 cm²
D.750 cm²
Challenging
A rectangular prism, Solid A, has dimensions 2 cm x 3 cm x 4 cm. A second prism, Solid B, is similar to Solid A and has a volume of 1,536 cm³. What are the dimensions of Solid B?
A.4 cm x 6 cm x 8 cm
B.6 cm x 9 cm x 12 cm
C.8 cm x 12 cm x 16 cm
D.10 cm x 15 cm x 20 cm
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