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Mathematics — CBSE Class 10 board question

Q1. [1]
A hemispherical bowl is made of steel of thickness 1 cm. The outer radius of the bowl is 6 cm. The volume of steel used (in $cm^3$) is :
  1. A $182\pi$
  2. B $\frac{182}{3}\pi$
  3. C $\frac{682}{3}\pi$
  4. D $\frac{364}{3}\pi$
Previously asked in CBSE board exam
2026 30/2/1 Q16
Generated by claude-sonnet-4-6 · 2026-06-15 10:34 · grounding rag
Model Answer

Outer radius $R = 6$ cm, inner radius $r = 6 - 1 = 5$ cm.

Volume of steel = Volume of outer hemisphere − Volume of inner hemisphere

$$= \frac{2}{3}\pi R^3 - \frac{2}{3}\pi r^3 = \frac{2}{3}\pi(6^3 - 5^3) = \frac{2}{3}\pi(216 - 125) = \frac{2}{3}\pi \times 91 = \frac{182}{3}\pi \text{ cm}^3$$

Answer: (B) $\dfrac{182}{3}\pi$

Explanation

The key idea: the bowl is hollow, so subtract the volume of the inner hemisphere from the outer one. Thickness = 1 cm gives inner radius = outer radius − 1 = 5 cm. Use $V = \frac{2}{3}\pi r^3$ for a hemisphere. Many students mistakenly use full sphere formula — remember it's a hemispherical bowl, so use $\frac{2}{3}\pi r^3$.

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