Discussion

If a hemisphere has a curved surface area of 175cm² its radius is

Answer: A

The curved surface of a hemisphere is half a sphere's, so

\[ \text{CSA} = 2\pi r^{2} = 175 \]

\[ r^{2} = \frac{175}{2\pi} = \frac{175}{6.2832} = 27.85 \]

\[ r = \sqrt{27.85} = 5.28 \text{ cm} \]

Only the curved dome is asked for, so the flat base is excluded; using the total surface \( 3\pi r^{2} \) would give \( r = 4.31 \) cm instead.

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