casa»Length measurement: definition with examples

- What is the length?
- Units to measure length
- SI unit of length
- worked examples
- practice problems
- Common questions

Length is the term used to identify the size of an object or the distance from one point to another. For example, the length of a ruler given below tells us what the length of the ruler is.

## What is the length?

Length measurement can be defined as the act of identifying the length of objects in some standard or non-standard units. The ability to measure length is very important in our daily lives.

Suppose Mathew goes to a store with his friend and sees a beautiful picture frame that could be placed in his parents' bedroom. But how would you tell them the frame length? You can do this if you know the length in a certain unit, say 3 feet. In the image below, the frame length is 3 feet.

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## Units to measure length

We can measure the length of an object using different units like meter, centimetres, feet, inches or using span, span, etc. We classify the units of measurement of length into two types:

### 1. Non-standard length measurement units

Non-standard units do not have any fixed measurement in numbers. Measurements vary from person to person and from object to object.

For example, a boy and his father measure a square with their hands. Therefore, the length they will be will be different because a child's length is usually shorter than an adult's. Some of the non-standard units of length are span, span, finger width, string or string, etc.

### 1. lapse of hand

The wingspan is the maximum distance between the tips of the thumb and little finger. It's usually around 8 inches, but it depends on your hand.

### 2. Standing light

The wingspan is defined as the distance between the tip of the toe and the heel of the foot.

### 2. Standard length measurement units

The default units are predefined and do not change from person to person or from object to object. Suppose there are two people measuring the length of a pencil with a ruler. If they use the standard units, they'll get the same value. Some examples of length measurements using standard units are centimeters, meters, kilometers, inches, feet, yards, etc.

We can divide the standard units of measurement of length into two types:

### 1. Metric System

The metric system includes kilometer, hectometer, dekameter, meter, decimeter, centimeter, and millimeter. There is a relationship between these units. The basic unit is the meter. The relationship of any other unit to the base unit (meters) is given below:

- 1 kilometer (km) = 1000 meters (m)
- 1 hectômetro (hm) = 100 m
- 1 decameter (dam) = 10 m
- 1 decimeter (dm) = 1/10 m = 0.1 m
- 1 centimeter (cm) = 1/100 m = 0.01 m
- 1 millimeter (mm) = 1/1000 m = 0.001 m

### 2. Sistema Imperial

The imperial system includes feet, yards, inches, etc. The relationship is given by:

1 allowance = 3 pies

1 foot = 12 inches

### Metric to imperial system

1 meter = 3.28 cakes

1 meter = 39.37 inches

### Imperial to Metric System

1 inch = 2.54 centimeters

1 cake = 30.48cm

1 pé = 0,3048 m

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## SI unit of length

The S.I. It is an international system of measurements universally used in technical and scientific research to avoid confusion with units. The SI unit for measuring length is given in meters (m). The meter is the basic unit of length.

### 1. Rulers

Rulers have straight edges and are rigid. One side of the ruler has inch markings and the other side has centimeter markings. Rulers are good to use for shorter lengths, like the length of a pencil or notebook.

### 2. Measuring tapes

Measuring tapes are flexible straight edges with graduated markings. Since most measuring tapes only measure one system of units (US or Metric), you'll need to find one that uses the system of units you need. Since these tools can be bent, they are good for measuring the total length of an object that exists in more than one dimension (eg waist measurements, circumference of a block of wood, etc.).

### 3. Metric bars

Metric rods and gauges are the same in construction and length. Both have straight edges and are rigid. Meters measure all lengths up to 1 meter and meters measure all lengths up to 3 feet.

### 4. Odometers

Odometers are tools that measure long distances traveled by vehicles such as cars and bicycles. Pedometers measure long distances covered by a human or other living being while walking. These tools are good for measuring miles and kilometers, but they are professionally calibrated and work without user intervention.

## How to measure the length?

There are two sides to a rule. On one side we see centimeters/millimeters and on the other side we see inches. The following steps are required to measure the length of an object:

**Step 1:**Choose the unit in which you want to measure the length of an object. If you want a value in cm/mm, use the cm/mm side of the ruler. If you want the value in inches, use the inch side of the ruler.

**Step 2:**Find the 0 mark at one end of the ruler. Align the zero mark with the leading edge of the object to be measured.

**Stage 3:**Look at the endpoint of the object and note the value. For example, in the figure below, the length of the pencil is from 0 to 10 cm.

## worked examples

**Example 1: How long is the window (in feet) if a 12-inch ruler is placed 4 times in a row?**

**Solution**: A 12-inch ruler is placed 4 times.

So the length of the window is 12 ✕ 4 = 48 inches = 4 feet.

**Example 2:****What must be the minimum length (in cm) of a case for a 450 mm long pen to fit inside?**

**Solution:**1 mm = $\frac{1}{10}$ cm

450 mm = 45 cm

The minimum length of a pencil case must be more than 45 cm.

**Example 3: The door is 3 feet long. How many centimeters long is it?**

**Solution**: 1 foot = 12 inches

3 feet = 3 ✕ 12 = 36 inches

**Example 4:****Olive walked 100 meters from her house to the bookstore and Mark walked 300 meters from her house to his friend's house, who walked the farthest?**

**Solution**: 1 allowance = 3 pies

100 yards = 300 feet

So Olive walked 300 feet and Mark also walked 300 feet.

Both covered the same distance.

## practice problems

1

### Kim started walking from her house. He walked 2 km from his house to the park, 3,000 m from the park to the club and 10,000 cm from the club to his house. What total distance did he travel (in m)?

51 metros

5100m

51000m

None of those

Correctincorrect

The correct answer is: 5100 meters

Distância total = 2 km + 3000 m + 10 000 cm = 2000 m + 3000 m + 100 m = 5100 m

2

### How many 30 mm long rubbers will fit in a 13 cm box if they are placed in a straight line one after the other?

1

2

3

4

Correctincorrect

The correct answer is: 4

Length of an eraser = 30 mm = 3 cm

13$\div$3 = 4,33

Only 4 rubbers fit.

3

### Can you help Catherine find the pencil length?

12cm

13cm

10cm

9,5cm

Correctincorrect

The correct answer is: 12 cm

The length of a pencil = 13 cm - 1 cm = 12 cm

## Common questions

**What is the smallest length measurement using rulers?**

The smallest measure of length is the millimeter. We use millimeters if an object is very small, say the length of our fingernails, etc.

**What is the SI unit used to measure the length of an object?**

The SI unit for measuring the length of an object is meters, which is denoted by "m". It is also the base unit.

**What are two methods for measuring the length of an object?**

The two methods for measuring the length of an object are:

1. Direct method, in which we use standard units of measurement such as meters, yards, inches, etc.

2. Indirect method, in which we use non-standard units such as span, span, etc.