Question

in a cylinder, if radius is halved and height is doubled, the volume will be: a:same b:doubled c:halved d:four times

Answer 1

Solution:-
Case 1:-
Let the original radius and the height of the cylinder be 14 cm and 20 cm respectively.
So, the volume of the cylinder = πr²h
= 22/7*14*14*20
Original Volume of the cylinder = 12320 cu cm
Case 2:-
The radius is halved and the height is doubled then the radius and the height of the cylinder will be 7 cm and 40 cm respectively.
volume = πr²h
= 22/7*7*7*40
= 154*40
Volume = 6160 cu cm
Now, in case 2, the volume of the cylinder has become halved. 
So, if the radius of the cylinder is halved and its height is doubled then the volume will be halved.
So, the option (c) is correct.
Answer.