A sector of a circle of radius 7.2 cm which subtends an angle of 300∘ at the centre is used to form a cone. What is the radius of the base of the cone?
Worked solution (try it first)
The arc of the sector becomes the circumference of the base: 360300×2π×7.2=2πr.
Divide both sides by 2π: r=7.2×65=6 cm, option A.