Here, it is helpful to use the formulae for the volume of a cone and a cylinder. I am assuming we are dealing with a right cone and a right cylinder.
[tex]V_{cone}= \frac{1}{3} \pi r^2h[/tex] and [tex]V_{cyl}= \pi r^2h[/tex].
The volumes of both of these figures are equal to 34 cubic inches, as you said. Notice in our formulae, everything is identical EXCEPT that the volume of a cone is basically that of a cylinder divided by three. To reverse this, that is, to find the volume of the cylinder, we would multiply by 3. 34 cubic inches times 3 is 102 cubic inches.
I would like to add that sometimes these formulae seem totally arbitrary. But when you think about the cylinder like a circle with a rolled-up rectangle, you can see that the [tex] \pi r^2[/tex] part is the area of a circle, and the height is because it's three dimensional. To translate this into the volume of a cone is a bit trickier. It involves calculus... [tex] \int\ {x^2} \, dx = \frac{1}{3}x^3[/tex]. If that looks like nonsense to you, then you can just remember that a cone is kind of a pointy cylinder and must be smaller than a cylinder!
