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Question

The height and radius of cone are 4 cm and 3 cm respectively. Fnd the curved surface area of cone.


A

14π cm2

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B

16π cm2

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C

15π cm2

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D

12π cm2

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Solution

The correct option is C

15π cm2


Given, height of the cone, h = 4 cm
radius of the cone, r = 3 cm

As we revolve a right-angled triangle about its height, we will get a cone. Therefore, slant height is the hypotenuse of the corresponding right-angled triangle.
By using Pythagoras' theorem, we get,
Slant height, l=h2+r2 =42+32 =5 cm

Surface area of the cone = πrl
= π ×3 × 5
= 15π cm2


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