A hollow sphere of internal and external diameters 4 cm and 8 cm respectively is melted into a cone of base diameter 8 cm. The height of the cone is (a) 12 cm    (b) 14 cm     (c) 15 cm      (d) 18 cm

Explanation

To solve the problem, we need to find the height of the cone formed by melting the hollow sphere. Here’s a step-by-step solution:

### Step 1: Find the radii of the hollow sphere
The internal diameter of the hollow sphere is 4 cm, so the internal radius \( r_1 \) is:
\[ r_1 = \frac{4}{2} = 2 \text{ cm} \]
The external diameter of the hollow sphere is 8 cm, so the external radius \( r_2 \) is:
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