[275 sq. cm] A boy cut a sector containing an angle of 140° from a circle of radius 15 cm and he folded the secto

For Competitive Exams

A boy cut a sector containing an angle of 140° from a circle of radius 15 cm and he folded the sector into a cone. What is the curved surface area of the cone {$ \pi=\dfrac{22}{7} $}

572 sq. cm

527 sq. cm

275 sq. cm

257 sq. cm

Explanation:

Area of sector=$\dfrac{\theta}{360^{0}}$
Curved surface area of cone=$\pi$rl

Area of sector=Curved surface area of cone

$\dfrac{\theta}{360}\times \pi r^{2}$

=$\dfrac{140}{360}\times \dfrac{22}{7}\times 15 \times 15$

=$\dfrac{7}{18}\times \dfrac{22}{7}\times 15 \times 15$

=275$cm^{2}$

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