Discussion

The radius of a semi circle is 6.3 cm then its perimeter is?

Answer: B

The perimeter of a semicircle includes the straight diameter as well as the curved arc.

\[ P = \pi r + 2r = r(\pi + 2) \]

With \( \pi = \tfrac{22}{7} \), so \( \pi + 2 = \tfrac{36}{7} \):

\[ P = 6.3 \times \frac{36}{7} = 0.9 \times 36 = 32.4 \text{ cm} \]

The arc alone measures \( \pi r = 19.8 \) cm; leaving out the 12.6 cm diameter is the standard omission.

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