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Module 1. Mathematics

The surface area of a cone whose height is 10 cm and diameter is 8 cm is

  • 40pi cm2 .
  • 80pi cm2.
  • 120pi cm2 .

Explanation

With a base diameter of 8 cm the radius is 4 cm, and a height of 10 cm gives a slant height of sqrt(10^2 + 4^2). The curved (lateral) surface of a cone is pi r times the slant height, which works out close to 40pi cm2, so this is the intended figure. The larger options would require an unrealistically large slant height.

giovanni asking:

how?? the lateral surface of a cone??

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