Test Index

JAMB Mathematics 2020 Paper

© africaexams.com

Question : 32

Total: 40

A sector of circle of radius 7.2cm which substends an angle of 300

^o

at the centre is used to form a cone. What s the radius of the base of the cone?

8cm
9cm
6cm
7cm

Solution:

Concept:

The arc length of the sector becomes the circumference of the cone’s base.

Explanation:

Convert

300^\circ

to radians:

300^\circ = \frac{300\pi}{180} = \frac{5\pi}{3}

Arc length

= 7.2 \times \frac{5\pi}{3} = 12\pi

cm.

This arc length is the circumference of the cone’s base:

2\pi R = 12\pi

So

R = 6

cm.

Answer:

6

cm, option C.

© africaexams.com

Go to Question:

Prev Question

Next Question