A cone of radius 7 cm and slant height 15 cm was cut horizontally, resulting in a smaller cone and a frustum of a cone. If the ratio of the curved surface area of the upper and the lower part is 1 : 2, What will be the slant height of the frustum formed?
A cone of radius 7 cm and slant height 15 cm was cut horizontally, resulting in a smaller cone and a frustum of a cone. If the ratio of the curved surface area of the upper and the lower part is 1 : 2, What will be the slant height of the frustum formed? Correct Answer 15 - 5√3
Calculation:
C.S.A (small cone : frustum) = 1 : 2
∴ C.S.A (small cone : big cone) = 1 : 3
As we know, C.S.A of small cone/C.S.A of big cone = r2/R2 = l2/L2 = h2/H2
∴ slant height (small cone : big cone) = 1 : √3
A.T.Q
Slant height of big cone = 15 cm
∴ Slant height of small cone = 15/√3 = 5√3
Frustum's slant height = 15 - 5√3 cm
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Feb 20, 2025