Similarity and Congruence Learning Outcomes  Know when shapes are similar  Know when shapes are congruent  Use similarity to find the missing sides of 2-D shapes  Use congruency to find the missing sides of triangles  Compare areas and volumes of similar shapes

Similarity and Congruence Similar Triangles Similar triangles – all angles are the same, sides of different lengths but in constant ratio Triangles ABC and DEF are similar because: by subtraction Ratio of sides = DF = EF AC BC A B C D E F

Similarity and Congruence Similar Triangles Triangles ABC and DEF are similar Findi) AC ii) DE A B C D E F 46 x 5 9 y

Similarity and Congruence Similar Triangles Find x R X P QY x 3

Similarity and Congruence Comparing Areas & Volumes of Similar Shapes 1) 1m 2m The above two rectangles are similar. i)If the above area of the smaller rectangle is 20m 2 find the area of the larger rectangle. ii)If the area of the larger is 40m 2, find the area of the smaller. 2) 5 x The above two rectangles are similar. Find x. 50cm 2 32cm 2

Similarity and Congruence Comparing Areas & Volumes of Similar Shapes 3) The sides of two cubes are in the ratio 2 : 5 i)Write down the ratio of their area ii)Write down the ratio of their volume iii)Find the volume of the larger if the volume of the smaller cube is 10cm 3 Summary Length Ratioa : b Area Ratioa 2 : b 2 Volume Ratioa 3 : b 3

Similarity and Congruence Additional Notes

Similarity and Congruence Learning Outcomes: At the end of the topic I will be able to Can Revise Do Further         Know when shapes are similar  Know when shapes are congruent  Use similarity to find the missing sides of 2-D shapes  Use congruency to find the missing sides of triangles  Compare areas and volumes of similar shapes