Question

If a right triangle is rotated about one of its perpendicular sides, then the 3D shape obtained will be a _______.

• A. cylinder
  
• B. rectangular prism
  
• C. cube
  
• D. cone
  

Answer 1

The correct option is D cone


In the given figure, l is the slant height, h is the height, and r is the radius of the cone.
The dashed lines in the figure corresponding to h and r are perpendicular to each other.
So, the three sides corresponding to h, r, and l form a right triangle.
When we rotate a right triangle about one of its perpendicular sides (in this case about h), the 3D shape obtained is a cone as shown in the given figure.