### The perimeter of Square and Rectangle

- Perimeter of a square = a + a + a + a = 4a, where a is the length of each side.
- Perimeter of a rectangle = l + l + b + b = 2(l + b), where l and b are length and breadth, respectively.

### Area of Square & Rectangle

- Area of a square = side × side
- Area of a rectangle = l × b
- Area of parallelogram = base × corresponding height (altitude)

**Triangles as Parts of Rectangles**

The sum of the areas of the two triangles, into which a diagonal of a rectangle divides the rectangle, is the same as the area of the rectangle. Also, both the triangles are equal in area.

**Conversion of Units**

1cm =10 mm

1 cm^{2} = 100 mm^{2}

1 m^{2} = 100 × 100 = 10,000 cm^{2}

1 km^{2} = 1000 × 1000 = 1,000,000 m^{2}

1 hectare = 10,000 m^{2}

Area of Triangle = 1/2 × Base × Height (Altitude)

The distance around a circular region is known as its circumference.

Circumference of a circle = πd = π(2r) = 2πr. where d is diameter and r is the radius.

Area of a circle = πr^{2}

π = 22/7 or 3.14 (approximately).

NCERT Solutions