A student said the volume of a cylinder with a 7-inch diameter is two times the volume of a cylinder with

the same height and a 3.5-inch radius. What is the error?

The volume of the first is not 2 * volume of the second. They both have the same volume.

Step-by-step explanation:

The 2 cylinders described are identical. The diameter = 2 times the radius, so the radius of the first cylinder = 1/2 * 7 = 3.5 in, which is the same as the radius of the second one. Also the heights are the same so the volumes are the same too.

When you find the volume of the cylinder you square instead which isn't equal to multiplying so the answer will be more then doubled.