Enough to Find It?

Part of the Surface Area & Volume section of Coddy's Geometry journey. Lesson 15 of 62.

Before you calculate, ask whether the figure says enough. A cylinder's volume formula links three things: the volume, the radius and the height. Know any two and the third is fixed. Know only one and it is not.

$A cylinder with radius 3, height and volume unknown$

This cylinder has radius 3, and that is all. Its height could be 1, or 10, or anything: a short can and a tall pipe can share a radius. So the figure does not fix the height, and it does not fix the volume either. Had the caption given the volume, the height would follow from the formula.

An answer of No is not a failure to find it. It means no rule could find it, because many different solids fit everything the figure says.

Challenge

This cylinder's height is 6, and nothing else is labelled. Does the figure give enough to find its radius? Answer Yes or No, then press Check.

Try it yourself

$Is there enough information?$

Is there enough information?

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Surface Area & Volume

3Cylinders

Volume of a Cylinder Height From the Volume Radius From the VolumeEnough to Find It?Recap: Cylinders

6Spheres and Hemispheres

Volume of a Sphere Half a Sphere Radius From the Volume Sphere in a Cylinder Recap: Spheres

9Pyramids and Cones Outside

Surface of a Pyramid Slant Height First Surface of a Cone The Cone: Slant First Recap: Pyramid Surfaces

12Final Challenges

Final: The Clay Cone Final: The Water Tank Final: The Model Pyramid Final: The Tent Final: The Paint Can