Perimeter and area of simple shapes | Math basics

Around versus inside

Two questions about a room:

How much baseboard goes around the edge? That's the perimeter: the distance around a shape.
How much carpet covers the floor? That's the area: the amount of surface inside.

Perimeter is measured in units of length (ft, in., m). Area is measured in square units ( $\text{ft}^2$ , $\text{in}^2$ , $\text{m}^2$ ).

A rectangle $$5$$ in. by $$3$$ in. can be covered by $$3$$ rows of $$5$$ one-inch squares: $$15$$ squares, so its area is $15 \text{ in}^2$ .

A triangle is half of a rectangle with the same base and height, which is where the $\frac{1}{2}$ comes from.

Break a complicated shape into rectangles and triangles, or think of it as a big rectangle with a piece removed.

Quick check

What is the area of a rectangle $$8$$ cm by $$6$$ cm?

Quick check

What is the perimeter of a square with sides of $$7$$ ft?