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WAEC Mathematics 2011 Paper

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Question : 17

Total: 47

The height of a cylinder is equal to its radius. If the volume is 0.216

\pi

^{3}

. Calculate the radius.

0.46m
0.60m
0.87m
1.80m

Solution:

Concept:

The volume of a cylinder is

\pi r^2 h

. Since

h = r

, this becomes

\pi r^3

.

Explanation:

Given, volume

= 0.216\pi \ \text{m}^3

and

h = r

.

So,

0.216\pi = \pi r^2 \times r = \pi r^3

.

Dividing both sides by

\pi

, we get

r^3 = 0.216

.

Taking the cube root,

r = \sqrt[3]{0.216}

.

Since

0.6^3 = 0.216

, we have

r = 0.6 \ \text{m}

.

Answer:

The radius is

0.60 \ \text{m}

. (Option B)

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