What is volume?

• A. The distance around the boundary of a shape.
• B. The amount of space inside a three-dimensional object.
• C. The area of a surface.
• D. The ratio of two quantities.

Answer: (B)

Volume is the amount of space inside a three-dimensional object. It tells you how much stuff can fit inside or how much space the object occupies, and we measure it in cubic units like cubic centimeters or cubic meters (or liters for liquids). This makes sense because volume counts the interior, not just the surface or boundary. For a rectangular box, you find it by multiplying length, width, and height; for a cube it’s side length cubed; for a cylinder it’s pi times radius squared times height. For irregular shapes you can use water displacement to see how much space is taken up. Volume is different from area, which measures the size of a surface in two dimensions, and from perimeter, which is the distance around the edge. It’s also not a ratio, which compares two quantities. So the correct idea is that volume is the space inside a three-dimensional object.