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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. - CBSE Class 9 - Mathematics

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ConceptSurface Area of a Right Circular Cone

#### Question

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

#### 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

Is there an error in this question or solution?

#### APPEARS IN

RD Sharma Solution for Mathematics for Class 9 by R D Sharma (2018-19 Session) (2018 to Current)
Chapter 20: Surface Areas and Volume of A Right Circular Cone
Ex.20.10 | Q: 4 | Page no. 7
Solution The Height of a Cone is 21 Cm. Find the Area of the Base If the Slant Height is 28 Cm. Concept: Surface Area of a Right Circular Cone.
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