Q17 of 22 Page 258

From a circle of radius 15 cm, a sector with angle 216° is cut out and its bounding radii are bent so as to form a cone. Find its volume.


Given, radius of circle = r = 15 cm


angle of sector(α) = 216°


Also, slant height of cone will be equal to the radius of the circle(L) = 15 cm


Let the radius and height of cone be r’& h respectively.


So, Area of the sector from circle = Curved surface area of the cone




r’ = 9 cm



As, L2 = r’2 + h2


h2 = L2 – r’2


h2 = 152 – 92


h2 = 225 – 81


h2 = 144


h = 12 cm


So


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