Starter quiz
- When an object is enlarged by a scale factor of 2, the object and its image are __________.
- alternate
- congruent
- corresponding
- similar ✓
- supplementary
-
- A triangle is enlarged by a scale factor of 2. Which of the following measurements will remain invariant?
- the angles ✓
- the length of its base
- the length of its height
- its perimeter
-
- Which angles are always equal when found on figure containing parallel lines and a transversal?
- adjacent
- alternate ✓
- co-interior
- corresponding ✓
-
Which angle is corresponding with ∠ECD?- ∠ACE
- ∠CEH
- ∠FEC
- ∠GEF ✓
-
Which rectangle is not similar to rectangle R?- A
- B ✓
- C
-
Triangle B is an enlargement of triangle A. What is the scale factor?- 10
- 12 ✓
- 15
-
Exit quiz
Which triangle is not similar to the others?- A
- B ✓
- C
- D
-
The table shows the base and height of four rectangles. Which rectangle is similar to a rectangle that is 2 cm by 5 cm?- A
- B
- C
- D ✓
-
Which shape is similar to shape P?- A
- B ✓
- C
-
The length of EB is ______ cm.- '3' ✓
The length of CD is ______ cm.- '8' ✓
∆ABC is similar to ∆ACD. The value of is ______.- '24' ✓
Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- Two shapes are not similar if there is a pair of lengths with a different multiplicative relationship.
- Similar shapes are not always easy to spot visually.
- A ratio table can help you find the scalar and functional multipliers in similar shapes.
- The angle sizes do not change.
Common misconception
Pupils may find it difficult to match up corresponding measurements on two congruent shapes when they are in different orientations.
Look lengths which are between any pairs of known angles or look for angles which are between pairs of adjacent known lengths. Also, tracing paper could be used to reflect/rotate/translate one shape onto the other.
Keywords
Object - The object is the starting figure before a transformation has been applied.
Image - The image is the resulting figure after a transformation has been applied.
Similar - Two shapes are similar if the only difference between them is their size. Their side lengths are in the same proportions.
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