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WAEC Mathematics 2010 Paper

Question : 47

Total: 49

Solution:

Concept:

Area of remaining part = area of rectangle − area of semicircle cut off.

Explanation:

The rectangular cardboard has length

22\text{ cm}

and width

8\text{ cm}

So, area of rectangle

=22 \times 8 = 176\text{ cm}^2

The diameter of the semicircle is

14\text{ cm}

, hence its radius is

r=\frac{14}{2}=7\text{ cm}

Area of semicircle

=\frac{1}{2}\pi r^2 = \frac{1}{2}\times \frac{22}{7}\times 7 \times 7

This gives area of semicircle

=77\text{ cm}^2

Therefore, area of the remaining part

=176 - 77 = 99\text{ cm}^2

Answer:

99\text{ cm}^2

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