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Find the total surface area of a cone with radius 9 cm and height 12 cm, in terms of π.

Class 9Surface Area of a ConeMensuration

A216π $cm^{2}$
B81π $cm^{2}$
C135π $cm^{2}$
D189π $cm^{2}$

Step-by-Step Solution

l

= √

(81 + 144) = 15

. TSA = π

r (l + r)

= π ×

9 \times 24 = 216

π

cm^{2}

. (135π is only the curved part; 189π uses h instead of

l : 9 \times 21.

)

Answer: A) 216π

cm^{2}

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