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WAEC Mathematics 2022 Paper

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Question : 39

Total: 47

Find the volume of a cone of radius 3.5cm and vertical height 12cm. [Take π = 22/7]

15.5cm $^3$
21.0cm $^3$
142cm $^3$
154cm $^3$

Solution:

Concept:

The volume of a cone is found using the formula

V = \frac{1}{3}\pi r^2 h

.

Explanation:

Given: radius

r = 3.5\text{ cm}

, vertical height

h = 12\text{ cm}

, and

\pi = \frac{22}{7}

.

Substitute these values into the formula:

V = \frac{1}{3} \times \frac{22}{7} \times (3.5)^2 \times 12

First,

(3.5)^2 = 12.25

.

So,

V = \frac{22 \times 12.25 \times 12}{3 \times 7}

Simplify:

12 \div 3 = 4

and

12.25 \times 4 = 49

.

Then,

V = \frac{22 \times 49}{7} = 22 \times 7 = 154

Therefore, the volume is

154\text{ cm}^3

.

Answer:

154\text{ cm}^3

[Option D]

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