∑ DANEMATHICS
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Grade 8 · Geometry of 2D Shapes
Congruent & Similar 2D Shapes
MEMORANDUM
Name:
Class:
Date:
Mark
/ 16
Answer all questions. Show all your working — marks are awarded for method as well as the final answer. Teacher copy: accept any correct equivalent method.
- 1What does it mean if two shapes are congruent?(2)Same shape and same size — identical.✓✓ (2)
- 2What does it mean if two shapes are similar?(2)Same shape, different size: equal angles and sides in proportion.✓✓ (2)
- 3Are all congruent shapes also similar?(2)Yes — with a scale factor of 1.✓✓ (2)
- 4Are all similar shapes congruent?(2)No — only when the scale factor is 1.✓✓ (2)
- 5Two similar triangles: sides 5 cm and 8 cm; the matching side to 5 is 15 cm. Find the other.(2)Scale factor 3 → 8 × 3 = 24 cm✓✓ (2)
- 6A rectangle 4 cm × 6 cm is enlarged by scale factor 2. What are the new sides?(2)8 cm × 12 cm✓✓ (2)
- 7Triangle A: 3, 5. Triangle B: 9, 15. Similar?(2)9÷3 = 3 and 15÷5 = 3 → Yes, scale factor 3.✓✓ (2)
- 8Triangle A: 2, 4. Triangle B: 6, 10. Similar?(2)6÷2 = 3 but 10÷4 = 2,5 → No, ratios differ.✓✓ (2)
TOTAL: 16 marks