What 2 things do you always need to say to describe an enlargement?
The scale factor
Centre of enlargement
What does centre of enlargement mean?
The centre of enlargement is the place where you start enlarging the shape
What is a scale factor?
A scale factor is how many times enlarged
Explain how to work out the scale factor on a grid, and with no grid. Use diagrams you have screenshot from the myimaths lesson.
To work out the scale factor on a grid, count how many squares on one of the sides on the shape that hasn't been enlarged. Then count how many squares that are on the same side as the none enlarged one and see how many times you can times it by.
For example in the image below, shape A has 2 squares at the bottom side of the shape and shape B has 4 on the same side. This means that the scale factor is 2 because 2 x 2 =4
For example in the image below, shape A has 2 squares at the bottom side of the shape and shape B has 4 on the same side. This means that the scale factor is 2 because 2 x 2 =4
To work out the scale factor that isn't on a grid, we use project lines.
The black lines in the picture above are the project lines, we use them to help us to find out the scale factor. Use the centre of enlargement (X) to start. Draw lines from the centre of enlargement to each side and beyond. then measure with a ruler how far from the centre of enlargement to the end of each side is and then measure with a ruler from that side to the end of the enlarged side, if the none enlarged side is 3 and the enlarged side is 9 then the sclae factor will be 3. Check the other sides to make sure you are correct.
What happens to the angle sizes in the corner of the shape when you enlarge it?
The angles stay the same
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