Let us measure the length of the table with pencil and then with a paper clip. We get different answers.

Now, measure a book with your handspan and then ask your father to measure the same book using his handspan. You may not get the same answer. Because cubit, handspan or fingers are not standard units of measuring a length.

The length of body parts varies from a person to person. Your fathers handspan is bigger than yours.

We need to use fixed measures to find the length of the objects. The standard unit of length is metre.

The length of longer objects is measured in meters. The length of shorter objects is measured in centimeters.

We write centimeter as cm and meter as m.

**1 metre = 100 centimetres**

**1 m = 100 cm**

What is the standard unit of length?

We know some non-standard units of length like hand-span, cubit, etc., and also with standard units of length like meter and centimeter. We have seen a meter-rod used by a tailor. It is used to measure the length of a cloth. The length of a meter-rod is called meter.

Different people have different length of body parts. Therefore, we use standard units to measure length.

Standard unit for measuring length is metre (m).

We use different units to measure different objects depending on how large the length or distance is. The length of smaller objects like a pencil is measured in centimetres (cm). The length of the classroom or height of a tree are measured in metres (m). Distance between two cities is measured in kilometres (km).

Length is measured in meters and centimetres and longer distances in kilometres.

One meter is divided into hundred equal parts. One division of this meter is known as one centimeter. To measure the length of the postcard, notebook, etc. we use centimeters (cm).

The meter-rod is used to measure the length of cloth, height of a place and small distances like length and breadth of a field, depth of a well, height of a building, etc.

The main standard unit of length is **Meter**. The short form of meter is **‘m’**.

To measure the length of the saree, classroom, blackboard, etc. we use meters (m).

The 100^{th} of a meter is called centimeter. Centimeter is the smaller standard unit of length. The short form of centimeter is **‘cm’**.

We use it to measure smaller lengths, such as length and breadth of a book, length of a pen, etc.

Two types of scales are used by the students in a geometry box; one scale is of 30 centimeters length and the other is 15 centimeters long.

There are also long measuring tapes for measuring lengths. A meter-tape is used for tailoring work and it is one and a half meter long. There are some long measuring tapes about 50 meters and 100 meters long. Such tapes are used to measure big lengths such as length and breadth of a field or park, etc.

We use the unit **kilometer** to measure very long distance such as the length of a
road, distance between two cities, etc., The unit kilometer is equal to 1000
meters. In short kilometer is written as **‘km’**.

To measure distance from one place to another, i.e. from house to school; from school to hospital; from California to Florida, etc. We use kilometers (km).

Thus, we can conclude that there are three
main standard units of length, i.e., kilometer (km), meter (m) and centimeter
(cm). **Click here** to know about the relation between the three units of length.

Standard units are also known as the SI units, which stand for International System of Units.

We measure the length of a pencil or a book in centimeters. Height of a tree or a ladder is measured in meters.

Questions and Answers on Standard Unit of Length:

**1. Tick the best unit of measurement that you will choose to measure the length of following objects.**

**Answer:**

**1.** Ladder: m

Floor Lamp: m

Eraser: cm

Mattress: m

Battery: cm

Mobile: cm

**2. Choose the best unit that you will use to measure the following objects.**

(i) The length of swimming pool is measured in __________ (cm/m/km)

(ii) The distance between your house and school is measured in __________ (cm/m/km).

(iii) The length of study table is measured in __________ (cm/m/km)

(iv) The length of eraser is measured in __________ (cm/m/km).

**Answer:**

**2.** (i) m

(ii) km

(iii) m

(iv) cm

**● Related
Concepts**

**● ****Conversion
of Standard Unit of Length**

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