Correct Answer: Option D

Explanation

PQ = circumference of the base of the cone = 2πr

PQ = \(\frac{120}{360}\) × 2πr = \(\frac{120}{360}\) × 2 × \(\frac{22}{7}\) × 21 = 44 cm

∴ 44 = 2πr; 44 = 2 × \(\frac{22}{7}\) × r

44 = \(\frac{44}{7}\) r

r = 7 cm

OR

r = \(\frac{R\theta}{360}\) = \(\frac{21 \times 120}{360}\) = 7cm.

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