A tub is in the shape of a frustum of a cone. The radii of two circular ends of the tub are 105 cm and 42 cm. If the vertical height of the tub is 16 cm, what is its slant height?
- A. 63.5 cm
- B. 65 cm ✓
- C. 73.5 cm
- D. 75 cm
Correct Answer: B. 65 cm
Explanation
The slant height l of a frustum is given by l = \sqrt{h^2 + (R-r)^2}. Here, l = \sqrt{16^2 + (105-42)^2} = \sqrt{256 + 63^2} = \sqrt{256 + 3969} = \sqrt{4225} = 65\text{ cm}.
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