RD Sharma - Mathematics

Book: RD Sharma - Mathematics

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

Subject: Mathematics - Class 9th

Q. No. 5 of CCE - Formative Assessment

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5

If the radius and slant height of a cone are in the ratio 7 : 13 and its curved surface area is 286 cm2, find its radius.

We have


Let radius of cone = 7x


Let slant height = 13x


Curved surface area of cone = 286 cm2


= πrl = 286 , 22/7×7x×13x = 286


= x2 = 1


= x = 1


Hence radius of cone = 7×1 = 7 cm


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