Question

A cylinder whose radius is 4 in and whose height is 8 in has its radius doubled. how many times greater is the volume of the larger cylinder than the smaller cylinder.

Answer 1

@tomhue

Answer 2

sorry for lateness

Cylinder volume formula is:
\[V={\pi}r^2h\]
It's the area of a circle, multiplied by the height.

Your values for the small cylinder (we'll label it "a") are r=4 and h=8.
Va=pi*4^2*8
Va=pi*16*8
Va=128pi

Now, we want to double the radius to get the larger cylinder (we'll label it "b"). r=8 and h=8.
Vb=pi*8^2*8
Vb=pi*64*8
Vb=512pi

How many times greater is the volume of the larger cylinder than the smaller cylinder?

This is simple division. Vb/Va=your answer.