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O-LevelMathematicsMensuration4024/13 · May/June 2025 · Q206 Marks

OAB and OCD are sectors of circles, each with centre O and angle 60°. Sector OAB has radius 6 cm. Sector OCD has radius 9 cm. [Figure 20.1]

  1. (a)The perimeter of the shaded region is (aπ + b) cm. Find the value of a and the value of b.[3]
  2. (b)Calculate the area of the shaded region. Give your answer in its simplest form in terms of π.[3]

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Mark scheme

Marking points from the official mark scheme (May/June 2025). The mark or mark type is shown in brackets.

  1. [3] (a) [a=] 5, [b=] 6
  2. B2 for a = 5
  3. or M2 for (60/360) × 2π×9 - (60/360) × 2π×6[ + 2 × 3] oe
  4. or M1 for (60/360) × 2π×9 or (60/360) × 2π×6 oe
  5. [3] (b) (15π/2) or 7.5π oe
  6. M2 for (60/360) ×π×9² - (60/360) ×π×6² oe
  7. or M1 for (60/360) ×π×9² oe or (60/360) ×π×6² oe

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About this question

Topic
Mensuration, O-Level Mathematics (syllabus 4024). Structured question, 6 marks.
Source
O-Level Mathematics, May/June 2025 Paper 1 Variant 3, question 20.

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