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WAEC Mathematics 2019 Paper

Question : 25

Total: 50

^{\circ}

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

]

Solution:

Concept:

The length of an arc is the fraction of the circumference corresponding to the angle subtended at the centre.

Explanation:

The angle subtended at the centre is

\theta = 72^\circ

The radius of the circle is

r = 3.5

cm.

The formula for the length of an arc is:

\text{Arc length} = \frac{\theta}{360^\circ} \times 2\pi r

Substitute the given values:

\text{Arc length} = \frac{72}{360} \times 2 \times \frac{22}{7} \times 3.5

Simplify

\frac{72}{360} = \frac{1}{5}

and

\frac{22}{7} \times 3.5 = 11

\text{Arc length} = \frac{1}{5} \times 2 \times 11

\text{Arc length} = \frac{22}{5} = 4.4 \text{ cm}

Hence, the length of the arc is

4.4

cm.

Answer:

The correct option is C.

4.4

cm.

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