Question

7. Total surface area of a right circular cone whose
height and radius are respectively 21 m and 28 m is
equal to-
​

Answer 1

EXPLANATION.

Height of a right circular cone = 21m.

Radius of a right circular cone = 28m.

As we know that,

Total surface area of cone = πr(r + l).

⇒ l = √r² + h².

⇒ l = √(28)² + (21)².

⇒ l = √784 + 441.

⇒ l = √1225.

⇒ l = 35m.

Put the values in the equation, we get.

Total surface area of cone = πr(r + l).

⇒ 22/7 x 28 (28 + 35).

⇒ 22 x 4 (63).

⇒ 88 x 63 = 5544m².

Total surface area of cone = 5544m².

Answer 2

Given that :-

Height = 21 m

Radius = 28 m

To Find :-

TSA

Solution :-

We know that

H² = B² + P²

l² = r² + h²

l² = (28)² + (21)²

l² = 784 + 441

l² = 1225

l = √1225

l = 35

Now

TSA = πr(l + r)

TSA = 22/7 × 28(35 + 28)

TSA = 22 × 4 × 63

TSA = 5544 m²

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