SPM 2018 Add Maths Paper 2, Question 5Circular Measure

Solved on video in English and Bahasa Melayu · Form 5, Circular Measure · 5:17 video

The question

Mathematics Society of SMK Muhibah organised a competition to design a logo for the society. Diagram 3 shows the circular logo designed by Amar. The three blue coloured regions are congruent. It is given that the perimeter of the blue coloured region is 20π cm. [Use π = 3.142] Find (a) the radius, in cm, of the logo to the nearest integer, (b) the area, in cm², of the yellow coloured region.

SPM 2018 Add Maths Paper 2, Question 5: the question as drawn in Eduly's video5:17

Step 1

The boundary of the three congruent blue regions is made up of 6 equal circular arcs. Each arc has radius equal to the logo radius j and subtends an angle of 60° = π/3 radian at its centre.

Why this step

Each petal has 2 curved edges, so 3 petals give 6 arcs. Students often count only some of them, or use sectors instead of arcs.

6 more steps, each with the reason for it, in the full solution

Final answer

(a) 10 cm, (b) 75.54 cm²

Where students lose marks

Watch out: count all 6 arcs, subtract all 6 segments, use 3 triangles (not 6), and keep θ in radians.

Watch every step of this question solved on video (5:17), with the reason behind each step and a box that checks your own answer.

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No card. Every past-year question on video, in English and BM.

All questions in SPM 2018 Paper 2

Circular Measure: lessons and every past-year question

Baca dalam Bahasa Melayu

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