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The Height of a Cone is 21 Cm. Find the Area of the Base If the Slant Height is 28 Cm. - Mathematics

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Question

The height of a cone is 21 cm. Find the area of the base if the slant height is 28 cm. 

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Solution

Given that 

Slant height ‘l’ = 28 m. 

Height of cone (h) = 21cm 

∴ Radius of cone (r)=`sqrt(28^2-21^2)`      [by Pythagoras theorem] 

= `7sqrt(7cm)` 

∴ Area of base = `pir^2` 

= `22/7xx(7sqrt7)^2` 

= `22/7xx7xx7=1078 cm^2` 

 

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Chapter 20: Surface Areas and Volume of A Right Circular Cone - Exercise 20.1 [Page 7]

APPEARS IN

RD Sharma Mathematics [English] Class 9
Chapter 20 Surface Areas and Volume of A Right Circular Cone
Exercise 20.1 | Q 4 | Page 7
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