## What is length?

Length is the term used for identifying the size of an object or distance **from one endpoint to another end object. **

**OR**

**Length is a measure of how long an object is or the distance between two points. **

**Metric Unit of Length: **In the metric system, the basic unit of length is **meter.**

**Vocabulary:**

The most common metric units of length are:

- Kilometer
- Meter
- Centimeter
- Millimeter

**Note: –** All of the other metric units of length are defined in terms of the **meter. **

### Let us understand the metric units of length, what they are in actual.

#### Kilometer

Kilometer is the biggest metric unit of measurement.

The abbreviation for **kilometer** is **‘km’**

**1 kilometer **is equal to** 1000 meter**

**1 kilometer** length is the same which is **about 2 ½ times around the track.**

#### Meter

It is the base unit of measurement.

The abbreviation for** meter **is** ‘m’**

**1 meter **length is the same as the length of** a guitar, the height of a chair. **

#### Centimeter

The abbreviation for centimeter is** ‘cm’.**

**1 c**length is same like** length of an ant, the length of a dice.**

#### Millimeter

The abbreviation for** millimeter** is** ‘mm’.**

**1 millimeter **length is the same like** the thickness of a paper.**

We can also understand **1 mm **by thickness of **a dot.**

### Some basic customary unit of length and relation between

### Distance of Metric Units of Length (Approximate)

**1 kilometer**length is the same that is**about 2 ½ times around the track.**

**1 meter**length is the same as the**length of a guitar, the height of a chair.**

**1 centimeter**length is the same as the**length of an ant, the length of a dice**.

**1 mm**by thickness of**a dot.**

### Conversion between the metric units

To convert larger unit to a smaller unit, we need to multiply.

To convert a smaller unit to a larger unit, we need to divide.

1. 7 m = _____ cm.

2. 6600 cm = _____m.

3. 37 m = _____cm.

4. 66 cm = ____mm.

5. 5 ½ km = ___m.

**Solution: **

**1. 1 m = 100 cm **

So, 7 m = 7 × 100 = **700** cm

**2. 1 m = 100 cm or 100 cm = 1m **

So, 1 cm = 1 ÷ 100 m Now, for 6600 cm = 6600 ÷ 100 m = **66 m**

**3. 1 m = 100 cm**

Now, 37 m = 37 × 100 = **3700 cm**

**4. 1 cm= 10 mm **

66 cm = 66 × 10 = **660 mm**.

**5. Since 1 km = 1000m **

So, 5 ½ km = 5 ½ × 1000 m

= 5 × 1000 + ½ × 1000

= **5500 m**

### Examples

**Example 1:** Five books of height 7 cm 5 mm each are stacked over one another. What is the total height so obtained?

**Solution: **

Height of one book = 7 cm 5 mm

So, the total height obtained for such 5 books = (7cm 5 mm) × 5

= 35 cm 25 mm **(But 10 mm = 1 cm)**

**=** (35 cm + 2 cm) and 5 mm

= **37 cm 5 mm **

**Example 2: ** Mr. John bought a cloth of length 3890 cm. How much is the length in m and cm?

**Solution: **

Since, 1 m = 100 cm or 100 cm = 1 m

So, 1 cm = 1/100 m

Now, 3890 cm = 3890 ÷ 100

= **38 m 9 cm **

### Concept Map

### What have we learned

- Identify metric units of length.
- Use multiplication and division to determine metric units equivalencies
- Perform arithmetic calculations on metric units of length.
- Solve application problems involving units of length.