Length 1

In this article, we are going to learn about length. Our learning objectives would be:

1. Measuring Length in metres
2. Comparing and Ordering Lengths

Watch our video lesson!

Topic Recap:

Measuring Lengths Using Centimetres

The length of an object tells us how long or short it is. We can use a ruler or measuring tape to measure length. The unit used for length is centimetre (cm).

The length of the pencil is 12 cm.

Remember to always measure your objects from the zero mark.

Example:

What is the length of the eraser?

Solution:

In order to find the length of the eraser, we will have to use: 

End value \(-\) Start value \(=\) Actual Length

Length of the eraser 

\(\begin{align}​​ &= 7 \text{ cm} - 3 \text{ cm}\\[2ex] &= 4 \text{ cm} \end{align}\)

The length of the eraser is 4 cm.

Answer:

4 cm

Question 1:

What is the length of the ribbon?

1. 5 cm
2. 8 cm
3. 13 cm
4. 14 cm

Solution: 

Length of the ribbon 

\(\begin{align}​​ &= 13 \text{ cm} - 5 \text{ cm}\\[2ex] &= 8 \text{ cm} \end{align}\)

Answer:

(2) 8 cm

Comparing And Ordering Lengths 

We can compare the length of objects.

The red stick is 8 cm long.
The yellow stick is 5 cm.
The blue stick is 3 cm. 

The yellow stick is longer than the blue stick.
The yellow stick is shorter than the red stick.

Therefore, the red stick is the longest and the blue stick is the shortest.

Question 1:

Order the objects from the shortest to the longest.

1. Paper clip, paintbrush, pen
2. Paper clip, pen, paintbrush
3. Paintbrush, pen, paper clip
4. Paintbrush, paper clip, pen

Solution: 

Length of the paintbrush \(= 14 \text{ cm}\)

Length of the pen

\(\begin{align}​​ &= 13 \text{ cm } – 2 \text{ cm}\\[2ex] &= 11 \text{ cm} \end{align}\)

Length of the paper clip

\(\begin{align}​​ &= 4 \text{ cm } – 1 \text{ cm}\\[2ex] &= 3 \text{ cm} \end{align}\)

The paper clip is the shortest and the paintbrush is the longest. 

Answer:

(2) Paper clip, pen, and paintbrush

1. Measuring Lengths In Metres

Another unit used for length is metre (m). We use metres to measure longer objects.

\(100 \text{ cm} = 1 \text{ m}\)

We measure larger items like doors, walls, refrigerators, sofas and beds in metres (m).

The length of the whiteboard is about 3 m.

Question 1:

Look at the sofa.

A. The sofa is __________ than 1 m long.

1. More
2. Less

Answer:

(1) More

B. The length of the sofa is about __________ m.

1. 1
2. 2
3. 3
4. 4

Answer:

(2) 2

Question 2:

The car is about __________ m long.

Answer:

5 m

Question 3:

The height of my bedroom door is about __________ m tall.

1. 1
2. 2
3. 3
4. 4

Answer:

(2) 2

2. Comparing And Ordering Lengths

The grid below has an interval of 1 m.

1. The length of the motorcycle is 2 m.
    
2. Length of the truck
   \(\begin{align}​​ &= 8 \text{ m } – 1 \text{ m}\\[2ex] &= 7 \text{ m} \end{align}\)
   The length of the truck is 7 m. 
    
3. Length of the van
   \(\begin{align}​​ &= 8 \text{ m } – 2 \text{ m}\\[2ex] &= 6 \text{ m} \end{align}\)
   The length of the van is 6 m.
    
4. Difference between van and motorcycle
   \(\begin{align}​​ &= 6 \text{ m } – 2 \text{ m}\\[2ex] &= 4 \text{ m} \end{align}\)
   The motorcycle is 4 m shorter than the van.
    
5. Arranging the vehicles from the longest to the shortest, we have:
   Truck, Van, Motorcycle

Question 1:

Look at the objects.

A. The length of the table is about __________ m.

1. 1
2. 2
3. 3
4. 4

Solution: 

Length of the table

\(\begin{align}​​ &= 3 \text{ m } – 0 \text{ m}\\[2ex] &= 3 \text{ m} \end{align}\)

Answer:

(3) 3

B. The length of the wall painting is about __________ m.

1. 1
2. 2
3. 3
4. 4

Solution: 

Length of the wall painting 

\(\begin{align}​​ &= 5 \text{ m } – 4 \text{ m}\\[2ex] &= 1 \text{ m} \end{align}\)

Answer:

(1) 1

C. The length of the bed is about __________ m.

1. 1
2. 2
3. 3
4. 4

Solution: 

Length of the bed 

\(\begin{align}​​ &= 8 \text{ m } – 6 \text{ m}\\[2ex] &= 2 \text{ m} \end{align}\)

Answer:

(2) 2

D. Arrange the objects in order of their lengths. Start with the shortest.

1. Table, bed, wall painting
2. Wall painting, bed, table
3. Table, wall painting, bed

Solution:

The bed is the shortest and the wall painting is the longest.

Answer:

(2) 

Question 2:

Look at the objects.

A. The tree is __________ m taller than the lamppost.

1. 5
2. 2
3. 10
4. 4

Solution: 

Height of the lamppost \(= 3 \text{ m}\)

Height of the tree \(= 5 \text{ m}\) 

Difference in height between the tree and the lamppost

\(\begin{align}​​ &= 5 \text{ m} - 3 \text{ m}\\[2ex] &= 2 \text{ m} \end{align}\)

Answer:

(2) 2

B. Arrange the objects in order of their heights. Start with the tallest.

1. Lamppost, shophouse,tree
2. Lamppost, tree, shophouse 
3. Shophouse, tree, lamp post

Solution:

The shophouse is the tallest and the lamppost is the shortest.

Answer:

(3) Shophouse, tree, lamp post

Question 3: 

The table shows the heights of 3 different buildings.

A. Building A is __________ m shorter than Building B.

1. 6
2. 24
3. 34
4. 36

Solution: 

Difference in height between Building A and Building B

\(\begin{align}​​ &= 270 \text{ m } – 246 \text{ m}\\[2ex] &= 24 \text{ m} \end{align}\)

Answer:

(2) 24

B. Arrange the buildings from the tallest to the shortest.

1.  Building A, Building B, Building C
2.  Building A, Building C, Building B
3.  Building B, Building C, Building A

Answer:

(3)

Challenge Yourself!

Question 1:

The traffic light is about __________ m tall.

1. 3 cm
2. 3 m
3. 30 cm
4. 30 m

Solution: 

3 cm and 30 cm are too short for the height of a traffic light. 30 m is too tall for the height of a traffic light. The height of the girl is about 1 m. So, the closest possible height of a traffic light is about 3 m.

Answer:

(2) 3 m

Question 2:

Route A is shorter than Route B. Route C is longer than Route B. Route D is longer than Route B but shorter than Route C.

Which is the longest route?

1. Route A
2. Route B
3. Route C
4. Route D

Solution: 

Draw to help you visualise the information above:

A _________________

B ________________________

C ________________________________________

D __________________________________

Answer:

(3) Route C