RD Sharma - Mathematics

Book: RD Sharma - Mathematics

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

Subject: Mathematics - Class 9th

Q. No. 7 of Exercise 20.1

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7

Find the total surface area of a cone, if its slant height is 21 m and diameter of its base is 24 m.

We have,


Slant height of cone(l ) = 21 m


Radius of cone ( r )= 12 m


Total surface area = πr2+ πrl= πr(r+l)


= ×12(12+21) m2


=×12×33 cm2=1244.57 m2


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