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Ex 13.4, 2 - The slant height of a frustum of a cone is 4 cm - Ex 13.4

  1. Chapter 13 Class 10 Surface Areas and Volumes
  2. Serial order wise
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Ex 13.4, 2 The slant height of a frustum of a cone is 4 cm and the perimeters (circumference) of its circular ends are 18 cm and 6 cm. Find the curved surface area of the frustum. We know that Curved surface area of frustum = ๐œ‹(๐‘Ÿ1+๐‘Ÿ2)๐‘™ Here l = 4 cm We need to find r1 & r2 Now, Curved surface area of frustum = ๐œ‹(๐‘Ÿ1+๐‘Ÿ2)๐‘™ = ๐œ‹(9/๐œ‹+3/๐œ‹)ร—4 = ๐œ‹((9 + 3)/๐œ‹)ร—4 = ฯ€ร—12/๐œ‹ร—4 = 48 cm2 Hence, curved surface area of frustum = 48 cm2

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