Area And Perimeter

Perimeter is the distance all the way around the edge of a shape, and area is the amount of flat space it covers. Together they answer everyday questions: how much fencing a field needs, how much paint covers a wall, how much carpet fits a room. Once you know a handful of formulas, the four most common straight-sided shapes become quick and reliable.

In this lesson you will calculate the perimeter and area of rectangles, triangles, parallelograms and trapeziums. The formulas are short, but each one hides a subtlety about which length to use. The single most important idea is that area always uses the perpendicular height, never a slanted side, and this lesson makes that habit stick.