WAEC - Mathematics (1992 - No. 14)
The angle of a sector of a circle of radius 8cm is 240°. This sector is bent to form a cone. Find the radius of the base of the cone.
16/3cm
15/3cm
16/5cm
8/3cm
16/10cm
คำอธิบาย
L = θ/360 x 2πR = 240/360 x 2 x 22/7 x 8/1 ... (1)
This must be equal to the circumference of the circle which is 2πr = 44R/7 .... (2)
equate (1) and (2)
r = 16/3 = 5\(\frac{1}{3}\)