11.5 Spheres and Hemispheres

Key Formulas

Solved Examples

Step 1

Inner radius $r = 5$ cm. Thickness $t = 0.25$ cm.

Step 2

Outer radius $R = r + t = 5 + 0.25 = 5.25$ cm.

Step 3

Outer CSA = $2\pi R^2$ .

Step 4

$= 2 \times \frac{22}{7} \times 5.25 \times 5.25$ .

Step 5

$= 44 \times 0.75 \times 5.25$ .

Step 6

$= 33 \times 5.25 = 173.25 \text{ cm}^2$ .

Final Answer

173.25 cm²

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