Question

A student said the volume of a cylinder with a 3 inch diameter is two times the volume of a cylinder with the same height and a 1.5 radius, what is the error?

Answer 1

so
volume=height times pi times radius^2
v=(h)(pi)(r^2)
so we shall see if it is true
r=3 and r=1.5
(h)(pi)(3^3)=2 times (h)(pi)(1.5^2)
we can divide both sides by hpi
3^3=2 times 1.5^2
9=2 times 2.25
9=4.5
false

the errror was that the person didn't take into account the squareing part in the volume formula