Key Points - Perimeter and Area

- Perimeter is the distance around a closed figure whereas area is the part of plane occupied by the closed figure.
- Area is the measure of the part of plane or region enclosed by it.
- We have learnt how to find perimeter and area of a square and rectangle in class 6.
They are:
(a) Perimeter of a square = 4 × side
(b) Perimeter of a rectangle = 2 × (length + breadth)
(c) Area of a square = side × side
(d) Area of a rectangle = length × breadth
- Area of a parallelogram = base × height
- Area of a triangle = 1/2 * base * height
- Area of equilateral triangle = sqrt(3)/4 * 9side)^2
- The distance around a circular region is known as its circumference.
- The ratio of circumference and diameter of a circle is a constant is denoted by π (pi).
- Circumference of a circle = πd, where d is the diameter of a circle and π = π / 7  or 3.14 (approximately).
- Area of a circle = πr 2 , where r is the radius of the circle.
- Based on the conversion of units for lengths, studied earlier, the units of areas can also be converted: 1 cm2 = 100 mm2
1 m 2 = 10000 cm 2 ,
1 hectare = 10000 m 2