🧮 The Math Factory
Q.If the base radius of a right circular cone is 3 cm and the height is 4 cm, then the lateral surface area of the cone will be. (a) \(10\pi \, cm^2\) (b) \(15\pi \, cm^2\) (c) \(12\pi \, cm^2\) (d) \(18\pi \, cm^2\)
Answer: B
The radius of the base of the cone \((r) = 3\) cm
And the height \((h) = 4\) cm

∴ The slant height of the cone \((l) = \sqrt{3^2 + 4^2} \) cm
\(= \sqrt{9+16} \) cm \(= \sqrt{25} \) cm \(= 5\) cm

∴ The lateral surface area of the cone \(= \pi rl\)
\(= \pi × 3 × 5 \, cm^2\) \(= 15\pi \, cm^2\)
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