Starter quiz
- A scale factor is the multiplier between __________ shapes that describes how large one shape is compared to the other.
- congruent
- similar ✓
- transformed
-
This sector is enlarged by scale factor . The angle in the image is ______°.- '60' ✓
- Each square on this coordinate grid is 1 unit long. This object is enlarged by a scale factor of 4 to make its image. Calculate the perimeter of the image.
- 20 cm
- 22 cm
- 66 cm
- 80 cm
- 88 cm ✓
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- A pentagon has a perimeter of 60 cm. The pentagon is enlarged by scale factor 7. The perimeter of the image is ______ cm.
- '420' ✓
The object is enlarged by a scale factor of to make the image. What is the perimeter of the image?- 9.9 cm
- 10 cm
- 18.8 cn
- 20 cm ✓
- 22 cm
-
- A shape is enlarged by a scale factor of to make its image. The perimeter of the image is 42 cm. The perimeter of the object is ______ cm.
- '28' ✓
Exit quiz
- A pentagon is enlarged by scale factor 2. What properties of the pentagon and its image are invariant?
- angles ✓
- area
- perimeter
- side lengths
- line symmetry ✓
-
Rectangle A has been enlarged to create rectangle B. Select the correct statements.- The perimeter of rectangle B is 3 × the perimeter of rectangle A ✓
- The perimeter of rectangle B is 9 × the perimeter of rectangle A
- The area of rectangle B is 3 × the area of rectangle A
- The area of rectangle B is 6 × the area of rectangle A
- The area of rectangle B is 9 × the area of rectangle A ✓
-
- Rectangle A has been enlarged to create rectangle B. The area of rectangle B is ______ cm²
- '288' ✓
Trapezium B is an enlargement of trapezium A. Calculate the area of trapezium B.- 40 cm²
- 80 cm²
- 120 cm²
- 160 cm² ✓
- 200 cm²
-
- Match each linear scale factor to the area scale factor.
- Linear scale factor:⇔Area scale factor: ✓
- Linear scale factor:⇔Area scale factor: ✓
- Linear scale factor:⇔Area scale factor: ✓
- Linear scale factor:⇔Area scale factor: ✓
- Linear scale factor:⇔Area scale factor: ✓
- Linear scale factor:⇔Area scale factor: ✓
Shape S is an enlargement an enlargement of shape R. The area of shape R is 32 cm². The area of shape S is ______ cm².- '200' ✓
Worksheet
Presentation
Video
Lesson Details
Key learning points
- An enlargement means the object and image are similar.
- All lengths in the object have been multiplied by the scale factor.
- Using index laws, this means the area has been multiplied by the scale factor squared.
Common misconception
If the length of an image is 4 times as long as its object, then its area will also be 4 times as big.
If the scale factor between lengths is 4, then the area of the image will be 16 times as big. The scale factor between the length of an object and image is different to the multiplier that shows how the area of an object changes after enlargement.
Keywords
Similar - Two shapes are similar if the only difference between them is their size. Their side lengths are in the same proportions.
Invariant - A property of a shape is invariant if that property has not changed after the shape is transformed.
Enlargement - Enlargement is a transformation that causes a change of size.
Scale factor - A scale factor is the multiplier between similar shapes that describes how large one shape is compared to the other.