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WAEC Mathematics 2021 Paper

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Question : 30

Total: 49

A trapezium of parellel sides 10cm and 21cm and height 8cm is inscribed in a circle of radius 7cm. calculate the area of the region not covered by the trapezium.

84cm $^2$
80cm $^2$
30cm $^2$
94cm $^2$

Solution:

Concept:

The area outside the trapezium is found by subtracting the trapezium's area from the area of the circle.

Explanation:

Area of the circle:

\pi r^2

= \frac{22}{7} \times 7^2

= 154\ \text{cm}^2

Area of the trapezium:

\frac{(a + b)h}{2}

= \frac{(10 + 21) \times 8}{2}

= \frac{31 \times 8}{2}

= 124\ \text{cm}^2

Required area: Area of circle

-

Area of trapezium

= 154 - 124

= 30\ \text{cm}^2

Answer:

30\ \text{cm}^2

Correct option: C

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