Question

The total surface area of a hemisphere of radius 21cm using value of π=22 / 7 is ___
Please help​

Answer 1

$\pink\bigstar$ Question Given :

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• $\dashrightarrow$ The total surface area of a hemisphere of radius 21 cm using value of π = 22 / 7 is ?

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$\green\bigstar$ Required Solution :

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♢ Value Given to us :

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• $\dashrightarrow$ Radius of hemisphere = 21

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♢ Formula Used Here :

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• $\dashrightarrow$ TSA of hemisphere = 3πr²

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♢ Putting Value in Formula :

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• $\dashrightarrow$ TSA = 3πr²

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• $\dashrightarrow$ TSA = 3 × 22 / 7 × 21 × 21

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• $\dashrightarrow$ TSA = 3 × 22 × 3 × 21 cm

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• $\dashrightarrow$TSA = 3 × 1,386 cm

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• $\dashrightarrow$ TSA = 4,158 cm²

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$\orange\bigstar$ Therefore :

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• $\dashrightarrow$ TSA will be 4,158 cm²

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Answer 2

Given

• The radius of hemisphere is 21 cm

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To Find

• The total surface area

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Solution

Formula to Find the Total Surface Area of Hemisphere → 3πr²

With the formula, let's substitute 'r' with the given value and use the value of π as 22/7

$\sf \implies 3 \times \dfrac{22}{7} \times (21)^{2}$

$\sf \implies 3\times \dfrac{22}{7} \times 441$

$\sf \implies 3\times 22 \times 63$

$\sf \implies 4158$

∴ The total surface area of a hemisphere of radius 21 cm is 4158 cm²

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Additional Information

• Total Surface Area of Cone → πr (r + l)
• Curved Surface Area of Cylinder → πrl
• Total Surface Area of Cylinder → 2πr (r + h)
• Curved Surface Area of Cylinder → 2πrh
• Total Surface Area of Hemisphere → 3πr²
• Curved Surface Area of Hemisphere → 2πr²

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