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 CCE - Formative Assessment

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7

Find the area of metal sheet required in making a closed hollow cone of base radius 7 cm and height 24 cm.

We have,


Base radius of cone = 7 cm


Height of cone = 24 cm


Slant height of cone l = √( r2+h2) = √(242+72) = √625 = 25 cm


Hence area of metal sheet required = total surface area of cone


= πr(l+r) = 22/7 ×7 (25+7)


=704 cm2


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