Surface Areas and Volumes
RD Sharma
CBSE
Grade 10
Question:
If the surface area of a sphere is $616\text{ cm}^2$, then its radius is:
(a) $7\text{ cm}$
(b) $14\text{ cm}$
(c) $3.5\text{ cm}$
(d) $21\text{ cm}$
Step-by-Step Solution
Key Concept: $4 \pi r^2 = 616 \Rightarrow 4 \times \dfrac{22}{7} \times r^2 = 616 \Rightarrow r^2 = 49 \Rightarrow r = 7\text{ cm}$.
$r^2 = \dfrac{616 \times 7}{88} = 49 \Rightarrow r = 7\text{ cm}$. [1.0 Mark]
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🎯 Official CBSE Marking Scheme:
Calculating radius $= 7\text{ cm}$: 1.0 Mark
Correct Answer: $7\text{ cm}$
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