Which statement describes a concave surface?

Which statement describes a concave surface?

• A. A surface that is curved outward in the middle.
• B. A surface that is curved inward in the middle.
• C. A flat surface.
• D. A surface that forms a cone.

Answer: (B)

Concave means the surface curves inward in the middle, like the inside of a bowl or spoon. You can picture the middle dipping down while the edges rise, giving that hollow shape. The other descriptions don’t fit: curved outward in the middle is convex (the opposite of concave); a flat surface has no curvature; a cone’s surface is made of straight lines meeting at a point, so it isn’t described simply as inward-curving in the middle.

Concave means the surface curves inward in the middle, like the inside of a bowl or spoon. You can picture the middle dipping down while the edges rise, giving that hollow shape. The other descriptions don’t fit: curved outward in the middle is convex (the opposite of concave); a flat surface has no curvature; a cone’s surface is made of straight lines meeting at a point, so it isn’t described simply as inward-curving in the middle.