Question

The height and slant height of cone are 21 cm and 28 cm respectively . Find the area of a base of cone and volume of cone

Answer 1

l^2=r^2+h^2
784-441=r^2
r^2=58.090
base area of cone= 3.14*18.5 = 58.090
volume of cone=1/3πr^2h
=1/3*22/7*18.5*18.5*21
=22*18.5*18*.5
=7529.50

Answer 2

Hi there !

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Height of the cone ( h ) = 21 cm.

Slant height ( l ) = 28 cm.

From l² = b² + h², we have ;

⇒ r = √ l² - h²

⇒ r = √ 28² - 21²

⇒ r = √ 784 - 441

⇒ r = √ 343

⇒r = 7 √ 7 cm.

So,

Volume of cone = $\mathsf {\frac {1} {3}}$ π r² h

$⇒ \mathsf{\frac{1}{3} \times \frac{22}{7} \times 7 \sqrt{7} \times 7 \sqrt{7} \times 21 } \\ \\ ⇒ \mathsf{22 \times 49 \times 7} \\ \\ ⇒ \mathsf{7546 \: cm {}^{3} }$

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Thanks for the question!

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