JAMB 2016 Mathematics · Question 13
An arc of the length 16cm subtends an angle of 80o at the centre of the circle. Find the radius of the circle.
Options
- A.24cm
- B.28cm
- C.36cm
- D.32cm
Answer: C. 36cm
Explanation written with AI and checked against the answer key
Analyze the question: We're given an arc length (16π cm) and the angle it subtends at the centre (80°). We need the radius. Concept: Arc length is a fraction of the circumference: Arc length = (θ/360) × 2πr Solution: 16π = (80/360) × 2πr 16π = (2/9) × 2πr 16π = (4πr)/9 Divide both sides by π: 16 = 4r/9 Multiply both sides by 9: 144 = 4r r = 36 cm Check: (80/360) × 2π × 36 = (2/9) × 72π = 16π ✓ Tip: Simplify the angle fraction first (80/360 = 2/9). It makes the arithmetic much easier, and you can always check by plugging your radius back into the formula.AI can make mistakes. Report anything that looks wrong.
Past questions © the examination body (JAMB/WAEC/NECO). DeeepSolve is not affiliated with them. Rights holders: see /copyright.