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Mathematics

If the diameter of the base of cone is 10 cm and its height is 12 cm, then its curved surface area is

  1. 60π cm2

  2. 65π cm2

  3. 90π cm2

  4. 120π cm2

Mensuration

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Answer

Radius of base of cone (r) = Diameter2\dfrac{\text{Diameter}}{2}

= 102\dfrac{10}{2} = 5 cm.

Height (h) = 12 cm.

l=r2+h2=52+122=25+144=169=13 cm.\text{l} = \sqrt{r^2 + h^2} \\[1em] = \sqrt{5^2 + 12^2} \\[1em] = \sqrt{25 + 144} \\[1em] = \sqrt{169} = 13 \text{ cm}.

Curved surface area = πrl.

Putting values we get,

Curved surface area = π × 5 × 13 = 65π cm2.

Hence, Option 2 is the correct option.

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