A 120° sector of a circle of radius 21cm is bent to form a cone. What is the base radius of the cone?
-
A.
31/2cm -
B.
7cm -
C.
1O1/2cm -
D.
14cm -
E.
21cm
Correct Answer: Option B
Explanation
The length of the arc subtended by the sector of angle 120° = circumference of the base of the cone.
(frac{120}{360} times 2 times frac{22}{7} times 21 = 2pi r)
(44 = 2pi r)
(r = 22 div pi)
(r = 22 times frac{7}{22})
r = 7 cm