Class 8 Chapter 15: Area of Polygons

# Class 8 Chapter 15: Area of Polygons

## Important Formulas on Perimeter and Area

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

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

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

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

5.      Perimeter of a rhombus = 4 × length of a side.

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

7.      The circumference of a circle of radius r is 2Ï€r.

8.      The ratio of the circumference of a circle to its diameter is denoted using the notation ‘Ï€’.

9.      The approximate value of Ï€ is 22/7 or 3.14.

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

11. Area of a rectangle = length × breadth.

12. Area of a square = side × side.

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

14. The area of a circle of radius r is Ï€r2.

15. Area of a parallelogram = base × perpendicular height.

16. Area of a rhombus = 1/2 × product of its diagonals.

17. Area of a trapezium = 1/2 × sum of parallel sides × height.

18. Area of a quadrilateral = 1/2 × (one diagonal) × (sum of the perpendiculars to the diagonal from the opposite vertices).

19. Area of a polygon = Sum of the areas of various triangles and trapeziums into which the polygon is splitted.

20. 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.

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