This is a Level 3 Geometry activity from the Figure It Out Series.
A PDF of the student activity is included.
Click on the image to enlarge it. Click again to close. Download PDF (84 KB)
- Recognise changes in properties with enlargement.
- Overhead projector
- A large sheet of square grid paper
- Transparencies
- FIO, Level 3, Geometry, Growing Changes, page 24
Warn students not to move the overhead projector while it is switched on, or the bulb may blow.
If students are having difficulty with the triangle and the circle, you could start with a simple square, as shown in Activity One:
B is an enlargement of A. The scale factor is two.
Answers to Activity
Activity One
a. The shape stayed the same, and the vertices remained right angles.
b. The length of the sides and the area
Activity Two
a. Features that have stayed the same are the shape, the vertices, and the ratio of side lengths. Features that have changed are the length of the sides and the area.
b. Features that have stayed the same are the shape and the centre point of the circle. Features that have changed are the circumference, the radius, the diameter, and the area (all increased).