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
$\dfrac{\theta}{360}\times \pi r^{2}$
=$\dfrac{140}{360}\times \dfrac{22}{7}\times 15 \times 15$
=$\dfrac{7}{18}\times \dfrac{22}{7}\times 15 \times 15$
=275$cm^{2}$