10 questions · Form 2 Mathematics Bab 5: Circles
An arc subtends an angle of 60° at the centre of a circle of radius 21 cm. Find the length of the arc. (Take π = 227)
Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.
1. An arc subtends an angle of 60° at the centre of a circle of radius 21 cm. Find the length of the arc. (Take π = 227)
Answer: A
Arc length = (θ / 360°) × 2πr = (60360) × 2 × (227) × 21 = (16) × 132 = 22 cm.
2. What is the angle subtended by a diameter at the circumference of a circle?
Answer: C
The angle subtended at the circumference in a semicircle is always a right angle (90°).
3. In a cyclic quadrilateral ABCD, if ∠A = 85°, find the measure of the opposite angle ∠C.
Answer: B
Opposite angles of a cyclic quadrilateral sum up to 180°: ∠C = 180° - 85° = 95°.
4. A perpendicular drawn from the centre of a circle to a chord of length 16 cm bisects the chord. What is the length of each half?
Answer: B
A perpendicular line from the centre bisects the chord into two equal parts: 162 = 8 cm.
5. If the area of a circle is 154 cm², find its radius. (Take π = 227)
Answer: A
πr² = 154 => (227)r² = 154 => r² = 154 × (722) = 49 => r = 7 cm.
6. Calculate the area of a sector with a central angle of 90° in a circle of radius 10 cm. (Take π = 3.142)
Answer: A
Area of sector = (90360) × 3.142 × 10² = (14) × 314.2 = 78.55 cm².
7. Find the area of a circle with a diameter of 14 cm. (Take π = 227)
Answer: A
Radius r = 142 = 7 cm. Area = πr² = (227) × 7² = 154 cm².
8. What is the longest chord in a circle?
Answer: C
The diameter passes through the centre of the circle and connects two points on the circumference, making it the longest chord.
9. Find the perimeter of a semicircle with a radius of 7 cm. (Take π = 227)
Answer: B
Perimeter = Arc length of semicircle + Diameter = (πr) + 2r = ((227) × 7) + 2(7) = 22 + 14 = 36 cm.
10. Calculate the circumference of a circle with a radius of 7 cm. (Take π = 227)
Answer: B
Circumference = 2πr = 2 × (227) × 7 = 44 cm.