Perimeter and Area: Practice

Perimeter adds all four sides, or use the shortcut $P = 2(l + w)$.

$P = 2(7 + 4) = 2 \times 11 = 22 \text{ cm}$

Perimeter is a length, so the unit is centimetres.

Area of a square is the side squared.

$A = s^2 = 6^2 = 36 \text{ m}^2$

Area counts how many unit squares cover a shape, so it uses square units.

Square metres ($\text{m}^2$) is an area unit; plain metres, kilometres, and centimetres are length units used for perimeter.

Area of a triangle is half the base times the height.

$A = \frac{1}{2} \times 8 \times 5 = \frac{1}{2} \times 40 = 20 \text{ cm}^2$

Area of a parallelogram is base times the perpendicular height.

$A = b \times h = 9 \times 4 = 36 \text{ cm}^2$

A square has four equal sides, so divide the perimeter by $4$.

$s = \frac{20}{4} = 5 \text{ m}$

Multiply the number of rows by the number of squares in each row.

$A = 4 \times 6 = 24 \text{ square units}$

This is exactly why a rectangle's area is rows times columns.

A rectangle with all sides equal is a square, so $P = 4s$ (or $2(l+w)$).

$P = 2(5 + 5) = 2 \times 10 = 20 \text{ cm}$

Area of a triangle is half the base times the height.

$A = \frac{1}{2} \times 12 \times 10 = \frac{1}{2} \times 120 = 60 \text{ m}^2$

Use $P = 2(l + w)$.

$P = 2(8 + 6) = 2 \times 14 = 28 \text{ m}$

Area of a parallelogram is base times the perpendicular height.

$A = b \times h = 7 \times 3 = 21 \text{ m}^2$

Area of a rectangle is length times width.

$A = 3 \times 2 = 6 \text{ cm}^2$

The unit is square centimetres, because area is a count of unit squares.