Q. 575.0( 2 Votes )

# The radius of the base of a cone is 5 cm and its height is 12 cm. Its curved surface area is

A. 60π cm^{2}

B. 65 π

C. 30 π cm^{2}

D. none of these

Answer :

Given: The height of the cone is 12 cm.

The radius of the cone is 5 cm.

Curved surface area of a cone is : πrl (here r and l are radius and slant height respectively)

l = √(r^{2} + h^{2})

∴ πrl = πr√(r^{2} + h^{2})

Let S be the CSA of the cone.

∴ S = πr√(r^{2} + h^{2})

⇒ S = π × (5) × √((5)^{2} + (12)^{2})

⇒ S = π × (5) × √(25 + 144) = π × (5) × √(169)

⇒ S = π × (5) × 13 = 65π

∴ S = 65π cm^{2}

That is CSA of the cone is 65π cm^{2}

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