ACT Practice Question: Cylinders in Geometry

 
Here is a practice question on how the volume of a cylinder varies with its height and radius.

The radius of a right circular cylinder is doubled and the height of the cylinder is halved to form a new right circular cylinder. The volume of the new
cylinder is how many times the volume of the original cylinder?

1. $\quad \dfrac{1}{4}$
2. $\quad \dfrac{1}{2}$
3. $\quad 1$
4. $\quad 2$
5. $\quad 4$