Verify mobile number to view the solution
Solutions
The correct answer is option 3 i.e. 404.25 cm3
If a semi-circular shape is bent into a conical shape, then the radius of the semi-circle is equal to the slant height of the cone. and the length of the circumference of the semi-circle is equal to the perimeter of the base of the cone.
The volume of the cone = (1/3)πr2h
The slant height of the cone = 7√3 cm
Let the radius of the cone = R cm
The circumference of the semi-circle = the perimeter of the base of the cone
π(7√3) = 2πR
R = (7√3)/2
Using Pythagoras' theorem in the right-angle triangle in cone,
(Perpendicular height)2 = ( slant height)2 - (radius)2
= ( 7√3)2 - ( 7√3/2)2
= 147 - 147/4
= 147 × 3/4 = 441/4
Perpendicular height = 21/2
The volume of the cone
= (1/3)(22/7)( 7√3/2)2(21/2) = 404.25 cm3.