In daily life, terms like tall, wide, short, long, height, width, depth, and breadth all refer to length measurement. These words are used depending on different situations and orientations, but they all denote length.
Lengths can be measured using ropes of standard lengths. We can define fractional parts of a metre as follows:
These units share the following relationships:
Developing an estimation of length helps in comparing sizes in our surroundings without immediate measurement tools.
To measure small items like an eraser, a pencil, or a seed, we need a unit smaller than a metre. A standard metre scale is divided into 100 equal parts. The length of each part is called a Centimetre (cm).
The relationship between metres and centimetres is defined as:
If a scale is broken and does not start at $0$, we can still measure the length of an object by finding the difference between the starting mark and the ending mark on the scale.
$$\text{Length} = \text{Ending Reading} - \text{Starting Reading}$$
Lengths can be expressed using a combination of metres and centimetres. For example, a height of $120\text{ cm}$ can be written as $1\text{ m } 20\text{ cm}$ because:
$$120\text{ cm} = 100\text{ cm} + 20\text{ cm} = 1\text{ m } 20\text{ cm}$$
When we measure the boundary of a shape, we are finding its perimeter.
The length of the boundary of a closed object or shape is called its perimeter.
A dot grid with dots spaced $1\text{ cm}$ apart can be used to find the perimeter of various shapes by counting the number of $1\text{ cm}$ segments along the boundary of the shape.