RD Sharma - Mathematics

Book: RD Sharma - Mathematics

Chapter: 20. Surface Area and Volume of a Right Circular Cone

Subject: Mathematics - Class 9th

Q. No. 6 of CCE - Formative Assessment

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The height of a solid cone is 12 cm and the area of the circular base is 64π cm2. A plane parallel to the base of the cone cuts through the cone 9 cm above the vertex of the cone, the area of the base of the new cone so formed is

We have,

Height of cone = 12cm

Area of circular base = 64π cm2

Height from the vertex of small cone = 9 cm

π r2 = 64π

r2= 64

Radius of base = 8cm

From similarity triangle =

= R =

R = radius of small cone

Area of small cone = πr2 = π(6)2 = 36π cm2

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