1. In geometry, two objects are similar when one is a scale model of the other. SIMILAR SHAPES

2. These two triangles appear to be similar…. SIMILAR SHAPES

3. These two are NOT similar….

4. How do you check that triangles are similar? SIMILAR TRIANGLES

5. We need to compare CORRESPONDING sides…. SIMILAR TRIANGLES

6. ….or corresponding angles. SIMILAR TRIANGLES Corresponding angles will be equal.

7. Looking for a scale factor

8. 8 10 6 15 9 12 SIMILAR TRIANGLES These two triangles are similar. What is the scale factor?

9. 8 10 6 15 9 12 SIMILAR TRIANGLES We really only need to use one pair of corresponding sides. SF = 12 ÷ 8 = 1.5

10. SIMILAR TRIANGLES Are these triangles similar?

11. Does the following apply? Try this neat method... If this is true, similarity applies

12. Lets check... So these are not similar triangles

13. The two triangles are similar. Use the cross multiplying method to determine the missing value x. 12 X 15 18