Geometry: angles and angle properties — KCSE Mathematics

KCSE Mathematics · 104 practice questions · 4 syllabus objectives

38 easy37 medium29 hard

What You'll Learn

Key learning outcomes for this topic, aligned to the KNEC KCSE syllabus.

State and apply angle properties: angles on a straight line, vertically opposite angles, angles at a point, corresponding, alternate and co-interior angles

Calculate interior and exterior angles of regular and irregular polygons; state the sum of interior angles of an n-sided polygon = (n–2)×180°

Apply angle properties of parallel lines cut by a transversal to solve multi-step angle problems

Geometry: angles and angle properties

Sample Questions

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1
easySHORT ANSWER3 marks

The sum of the interior angles of a polygon is 720°. (a) Calculate the number of sides of the polygon. (2 marks) (b) State the name of the polygon. (1 mark)

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Part (a) — 2 marks
(n - 2) × 180 = 720 ⇒ n - 2 = 720/180 (1 mk)
n = (720/180) + 2 (1 mk)
Part (b) — 1 mark
Hexagon (1 mk)
2
easySHORT ANSWER4 marks

State the properties of angles formed when two parallel lines are cut by a transversal and illustrate how they can be used to find unknown angles. (4 marks)

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Part (a) — 2 marks
Corresponding angles are equal (1 mk)
Co-interior angles are supplementary (sum to 180°) (1 mk)
Part (b) — 2 marks
If one angle is known, corresponding angles can be identified as equal (1 mk)
If one angle is known, co-interior angles can be calculated as 180° minus the known angle (1 mk)
3
easySHORT ANSWER3 marks

In a triangle, the angles are in the ratio 2:3:4. Find the size of the largest angle. (3 marks)

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Part (a) — 3 marks
Let the angles be 2x, 3x, and 4x. The sum is 9x = 180° (1 mk)
Solve for x: x = 20° (1 mk)
Largest angle = 4x = 80° (1 mk)
4

Two parallel lines AB and CD are cut by a transversal EF. Angle AEF = 18°. Find, giving reasons, the size of: (a) angle CEF [1 mark] (b) angle EFD [1 mark] (c) angle EFC [1 mark]

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Why Practise Geometry: angles and angle properties?

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