Find the area of a circle whose diameter is 7 cm . [Take π=\;22/7 ]

Correct Answer is : 38 12 cm2\;\; 38\;1/2\ {cm}²3821 cm2

Correct Answer is : 38 12 cm2\;\; 38\;1/2\ {cm}²3821 cm2

Test Index

BECE Mathematics 2016 Paper

Question : 28

Total: 40

\pi=\;\frac{22}{7}

Solution:

Concept:

The area of a circle is found using

A = \pi r^2

, where the radius is half the diameter.

Explanation:

Diameter

= 7\ \mathrm{cm}

, so radius

r = \frac{7}{2}\ \mathrm{cm}

Substitute into

A = \pi r^2

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

Cancel one 7 in the numerator with the 7 in the denominator:

A = \frac{22 \times 7}{2 \times 2} = \frac{154}{4}

Simplify:

\frac{154}{4} = \frac{77}{2} = 38\frac{1}{2}\ \mathrm{cm}^2

Answer:

Option B:

38\frac{1}{2}\ \mathrm{cm}^2

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