Corresponding sides — Grade 7 Accelerated, what it means and where it is taught
Sides in matching positions in two similar figures.
Taught in Grade 7 Accelerated.
Where it is taught
What it rests on
Work through these first if this one does not settle.
- Similar figures — Same shape, different size: equal angles, proportional sides.
Practise this idea
5 questions in the course bank use Corresponding sides, in Proportional Reasoning with Scale Drawings, Congruence & Sequences of Transformations, Dilations & Similarity, Triangle Congruence Proofs.
Problem 1
Two similar triangles have corresponding sides 6 and 15. Find the scale factor from the smaller to the larger.
Worked answer
2.5
156 = 2.5
Problem 2
△ ABC ≅ △ DEF and AB = 7. Find DE.
Worked answer
7
AB corresponds to DE
Corresponding sides are equal
DE = 7
Problem 3
△ ABC ≅ △ DEF with AB = 3x - 4 and DE = 2x + 5. Find x.
Worked answer
9
3x - 4 = 2x + 5
x = 9
Check: 3(9) - 4 = 23 and 2(9) + 5 = 23 ✓
Problem 4
Which is always true for two similar figures?
- Corresponding angles are equal
- Corresponding sides are equal
- Perimeters are equal
- Areas are equal
Worked answer
Corresponding angles are equal
Angles never change under a dilation
Sides change by the factor k
So only the angle statement is always true
Problem 5
△ ABC ≅ △ DEF with AB = 3x + 1 and DE = 2x + 7. Find AB.
Worked answer
19
3x + 1 = 2x + 7, so x = 6
AB = 3(6) + 1 = 19