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A rectangle is a four-sided closed figure with four right angles and with opposite sides parallel and congruent.

A right angle is an angle that measures 90 degrees. A right angle is formed when two perpendicular lines meet. (See angle.)

Rounding gives you an approximate number if you don’t need an exact one. If 2,323 people attended a soccer game, about 2,000 people were there. If 2,857 people attended, about 3,000 were there. Round up if the number is halfway or more to the next highest number (2,500 is halfway between 2,000 and 3,000). Round down if the number is less than halfway.

A solid is a three-dimensional figure in geometry, like a cube, a cone, a prism, or a sphere.