Class 7 Chapter 16: Perimeter and Area

Important Concepts and Formulas

1.      The perimeter is the distance around a closed figure.

2.      Perimeter of a rectangle = 2 × (length + breadth).

3.      Perimeter of a square = 4 × length of a side.

4.      Perimeter of a triangle = sum of all its sides.

5.      The total distance around a circle is called its circumference.

6.      The circumference of a circle of radius r is 2πr.

7.      The ratio of the circumference of a circle to its diameter is denoted using the notation ‘π’.

8.      The approximate value of π is 22/7 or 3.14.

9.      Perimeter of a regular polygon = (Number of sides of polygon) × (length of a side).

10. The amount of the surface enclosed by a closed figure is called its area.

11. Area of a rectangle = length × breadth.

12. Area of a square = side × side.

13. Area of a parallelogram = base × height.

14. Area of a triangle = 1/2 × base × height.

15. The area of a circle of radius r is πr².

16. The perimeter is expressed in the same unit as the length and the breadth.

17. The units of area are square units, such as 1 cm² = 100 mm² ; 1 m² = 10,000 cm² ; 1 km² = 10,00,000 m² ; 1 hectare = 10,000 m² ; 1 acre = 4046.86 sq. m.