Triangles are similar if matching
angles remain the same size.
100º
30º
50º
100º
50º
30º
10º
50º
120º
10º
50º
120º
15
5x
Scale factor 3
5
3
4
x3
6
15
1
3
18
Scale factor 1/3
12
A
4
D
3
E
6
C
B
Triangle ABC is similar to triangle ADE.
DE is parallel to BC.
Calculate the length of BC
A
D
4
3
E
9
6
B
12
C
9x
3
3
AB & DE are parallel
A
5
Explain why ABC is similar to CDE
B
<CED = <BAC Alternate Angles
= <ABC Alternate Angles
= <ACB Vert Opp Angles
D
?
Triangle ABC is similar to Triangle CDE
E
Calculate the length of DE
A
5
AC corresponds to CE
Scale Factor = 2
B
B corresponds to DE
E = 2 x AB
E = 10cm
D
?
E