Question

Find the total surface area of a cone, if its slant height is 21 m

and diameter of its base is 24 m.​

Answer 1

Given

• A cone
• Slant height = 21 m
• Diameter of the base = 24 m

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To Find

• The Total Surface Area of a Cone

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Solution

Formula to find Total Surface Area of a Cone → πr (r + L)

Here r is the radius and L is the slant height of the cone.

Radius ⇒ Diameter ÷ 2

Radius ⇒ 24 ÷ 2

Radius ⇒ 12 m

∴ The radius is 12 m.

Total Surface Area of Cone ⇒ $\dfrac{22}{7} \times 12 \times (12 + 21)$

⇒ $\dfrac{22}{7} \times 12 \times 33$

⇒ $\dfrac{22}{7} \times 396$

⇒ $\dfrac{8712}{7}$

⇒ $1244.57$

∴ The total surface area of a cone, if its slant height is 21 m and the diameter of its base is 24 m is 1244.57 m²

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Answer 2

Answer:

Given

A cone

Slant height = 21 m

Diameter of the base = 24 m

___________________________

To Find

The Total Surface Area of a Cone

___________________________

Solution

Formula to find Total Surface Area of a Cone → πr (r + L)

Here r is the radius and L is the slant height of the cone.

Radius ⇒ Diameter ÷ 2

Radius ⇒ 24 ÷ 2

Radius ⇒ 12 m

∴ The radius is 12 m.

Total Surface Area of Cone ⇒ $\dfrac{22}{7} \times 12 \times (12 + 21)$

⇒ $\dfrac{22}{7} \times 12 \times 33$

⇒ $\dfrac{22}{7} \times 396$

⇒ $\dfrac{8712}{7}$

⇒ $1244.57$

∴ The total surface area of a cone, if its slant height is 21 m and the diameter of its base is 24 m is 1244.57 m²

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