# MENSURATION

## Heron's Formula of Class 9

The branch of mathematics that deals with measurement especially the derivation and use of algebraic formulae to measure the areas ,surface area , volumes and different parameters of geometric figure.

### Perimeter :

The perimeter of a plane figure is the length of its boundary. In case of a triangle or a polygon, the perimeter is the sum of the lengths of its sides.

### DIMENSION:

A dimension is a direction in which one can measure distance.  For example, “horizontal distance and vertical distance ” or “left and right” is a dimension.

Length is the size in one dimension.It could be the amount of string needed to cover a line.

Area is the size in two dimensions.It could be the amount of paper needed to cover a shape.

### Units of Perimeter :

The unit of perimeter is the same as the unit of length i.e. centimetre (cm), metre(m), kilometere (k m) etc.

1 centimetre (cm)     = 10 milimetre (mm)

1 decimetre (dm)     = 10 centrimetre

1 metre (m)     = 10 decimetre

= 100 centimetre

= 1000 milimetre

1 decamete (dam)    = 10 metre

= 1000 centimetre

1 hectometre (hm)     = 10 decametre

= 100 metre

1 kilometre (km)     = 1000 metre

= 100 decametre

= 10 hectometre