RD Sharma - Mathematics

Book: RD Sharma - Mathematics

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

Subject: Mathematics - Class 9th

Q. No. 8 of CCE - Formative Assessment

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Find the length of cloth used in making a conical pandal of height 100 m and base radius 240 m, if the cloth is 100π m wide.

We have ,

Height of conical pandal = 100m

Base radius of pandal = 240 m

Slant height l = √( r2+h2) = √2402+1002 =√67600 = 260 m

Curved surface area of cloth = πrl = π×260×240

Hence length of 100π m wide cloth = curved surface area of cloth/ width of cloth

= π×260×240 / 100π

= 26×24 = 624m

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