Perimeter and Area

Perimeter is the distance around a shape; area is the space it covers. Formulas for rectangles, squares and triangles.

Key ideas

Perimeter is measured in units of length (cm, m); area in square units (cm², m²).
To find the perimeter of any shape, add the lengths of all its sides.
Count squares to find area: each full square is 1 square unit; more than half a square counts as one.
A triangle drawn on the diagonal of a rectangle has half the rectangle’s area.
Shapes with the same area can have different perimeters, and the other way round.

Rectangle	perimeter = 2 × (l + b); area = l × b
Square	perimeter = 4 × side; area = side × side
Triangle	perimeter = a + b + c; area = ½ × base × height
Units	100 cm = 1 m; 1000 m = 1 km

Neeraj runs 8 rounds of a square park of side 150 m. How far does he run? Give the answer in km.

Working: one round 4 × 150 = 600 m; 8 rounds = 4800 m = 4.8 km

Answer: 4.8 km