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O-LevelMathematicsGeometry4024/12 · May/June 2018 · Q144 Marks

An irregular polygon has 22 sides.

  1. (a)Calculate the sum of all its interior angles.[2]
  2. (b)Two of the angles in the polygon are each 170°. The remaining 20 angles are equal to each other. Calculate the size of one of the 20 equal angles.[2]

Mark scheme

Marking points from the official mark scheme (May/June 2018). The mark or mark type is shown in brackets.

  1. [1] M1 for 180 × (22-2) oe or (180 - 360/22) × 22 oe
  2. [1] 3600
  3. [1] M1 for 2×170+20x = their 3600 or for (their 3600-2×170)÷20 oe
  4. [1] 163

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About this question

Topic
Geometry, O-Level Mathematics (syllabus 4024). Structured question, 4 marks.
Source
O-Level Mathematics, May/June 2018 Paper 1 Variant 2, question 14.

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