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A cone is constructed by rolling up a sector of a circle. The radius of the original sector becomes the cone's:
Answer & Solution
Correct answer: D.
1. When a sector is rolled into a cone, the two straight edges (radii of the sector) coincide along a slant line of the cone.
2. Each straight edge runs from the apex of the cone to a point on the base circle.
3. So the radius of the sector becomes the slant height of the cone.
4. The arc of the sector becomes the base circumference, not the base radius itself.
5. Hence slant height = sector radius.
_Source: SCERT Kerala Std X Mathematics Part-2, Chapter 7-8 (pp 180-199, 2019 ed.)._
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