Length
Long, Short, Tall, and Comparing Lengths
What is Long and Short, Tall and Short?
Long and short are words used to talk about the distance of an object from one end to the other when it is lying down flat. Tall and short are words used to talk about how high an object is from the ground to the top when it is standing up straight. Comparing lengths means placing objects side-by-side to find out which one stretches out further or reaches higher.
Think about these simple examples:
* A blue skipping rope is long, but a yellow crayon is short.
* A beautiful giraffe is tall, but a cute little puppy is short.
When we compare lengths, we must line up the starting ends perfectly at the same base line.
* If something stretches out more than another, it is longer.
* If something looks smaller in length, it is shorter.
* If something reaches higher up into the air, it is taller.
| Comparison Type | Position | Word for Big | Word for Small | Real-Life Example |
|---|---|---|---|---|
| **Length** | Lying Flat | **Long** / **Longer** | **Short** / **Shorter** | A long train vs. a short car. |
| **Height** | Standing Up | **Tall** / **Taller** | **Short** / **Shorter** | A tall building vs. a short tent. |
Example 1: Look at a long yellow bus and a short family car parked side-by-side. Which vehicle is shorter?
Solution:
Think about how much space each vehicle takes on the road.*
The school
Think about how much space each vehicle takes on the road.*
The school bus stretches out very far from front to back.*
The family car is small and takes up much less space.*
The one that takes up less space horizontally is the shorter one.*
Answer: Family car
Example 2: A father zebra stands 6 feet high from the ground. His baby zebra stands 3 feet high from the ground. Who is taller?
Solution:
Compare the heights of the two animals standing up.*
Father zebra height = 6 feet.*
Baby zebra height = 3 feet.*
Compare the numbers: 6 is greater than 3 (6 > 3).*
The higher number means the position is higher up, making the father zebra taller.*
Answer: Father zebra
Example 3: Pencil A is longer than Pencil B. Pencil B is longer than Pencil C. If you arrange them in a line starting from the shortest, which pencil comes first?
Solution:
Let us look at the clues given: A > B and B > C.*
This means A is the biggest, B is in the middle, and C is the smallest.*
The order from longest to shortest is: Pencil A -> Pencil B -> Pencil C.*
The question asks to arrange them starting from the shortest.*
The order from shortest to longest is: Pencil C -> Pencil B -> Pencil A.*
Answer: Pencil C
Key Points
- We use long and short for objects lying flat down on a surface.
- We use tall and short for objects standing straight up from the ground.
- To compare objects correctly, always line up their bottoms at the exact same base line.
- Longer means an object has more length than another object.
- Taller means an object has more height than another object.
Non-Standard Units of Measurement
What is a Non-Standard Unit of Measurement?
A non-standard unit of measurement is an everyday object that we use to count and measure how long or tall something is. Before people had standard plastic rulers, they used their own bodies and small items around them to measure things!
Common non-standard items include:
* Handspan: The distance from the tip of your thumb to the tip of your pinky finger when stretched out wide.
* Cubits: The length from your pointy elbow to the tip of your middle finger.
* Paces: The size of one big walking step.
* Paperclips or blocks: Small school items lined up end-to-end along an object.
Because people have different hand sizes, measuring with non-standard units can give different numbers! A teacher's handspan is much larger than a first-grader's handspan.
| Unit Name | What part of the body/item? | Used to measure what? |
|---|---|---|
| **Handspan** | Stretched fingers | Length of a school notebook or desk face. |
| **Pace** | Walking step | Length of a classroom floor or playground path. |
| **Paperclip** | Small metal clip | Length of a pencil or a paint brush. |
| **Cubit** | Elbow to finger tip | Length of a kitchen table or a wooden bench. |
Example 4: Timmy measures his teacher's desk using wooden blocks. He places 8 blocks in a perfect line from left to right. How long is the desk in blocks?
Solution:
To find the length, count
To find the length, count the total number of non-standard units used.*
The blocks are lined up perfectly from end to end.*
The total count of blocks used is 8.*
Answer: 8 blocks
Example 5: Jenny measures her storybook using paperclips. It is exactly 5 paperclips long. Her friend Sam measures the same book using longer crayons, and it takes 3 crayons. Why are the numbers different?
Solution:
Paperclips and crayons are non-standard units of different sizes.*
A crayon is much longer than a small paperclip.*
Because a crayon is longer, you need fewer of them (3) to cover the same book length compared to paperclips (5).*
Answer: Crayons are longer than paperclips.
Example 6: A chalkboard is 10 handspans long. If Ron's handspan can hold exactly 2 small plastic erasers inside it, how many erasers long is the chalkboard?
Solution:
Length of chalkboard = 10 handspans.*
Each 1 handspan = 2 erasers.*
To find the total number of erasers, multiply or add 2 ten times: 10 \times 2 = 20.*
Let us double check: 2+2+2+2+2+2+2+2+2+2 = 20.*
Answer: 20 erasers
Key Points
- Non-standard units include body parts like handspans, cubits, and paces.
- Small identical objects like paperclips, blocks, and counters can also be used to measure.
- When measuring, leave no gaps and do not let the objects overlap each other.
- Smaller units give a larger number count for the same object length.
- Larger units give a smaller number count for the same object length.
Introduction to Centimetres
What is a Centimetre?
A centimetre is a fixed, standard unit used to measure length worldwide. We write it as cm for short. Because it is a standard unit, 5 centimetres is exactly the same length whether it is measured by a child, a parent, or a scientist!
To find centimetres, we use a tool called a ruler.
* The small spaces and numbers marked on your school ruler show centimetres.
* Your little finger is about 1 centimetre wide!
* A standard staple pin is also about 1\text{ cm} wide.
* How to Use a Ruler to Measure:
* Step 1: Place the left tip of your object exactly at the 0 mark on the ruler.
* Step 2: Keep the object flat and straight along the edge of the ruler.
* Step 3: Look at the other end of the object and find the closest number. That number tells you its length in cm!
| Unit Full Name | Short Form | Common Tool | Real-World Size Estimate |
|---|---|---|---|
| **Centimetre** | **cm** | Ruler / Measuring Tape | The width of a small fingernail or a bean. |
Example 7: Anna places her new pink eraser on a ruler. The left end is at the 0 mark and the right end stops directly at the number 4. How long is the eraser?
Solution:
Check the starting po
Check the starting point on the ruler: it is at 0, which is correct.*
Look at where the object ends on the ruler scale.*
The eraser edge matches up with the number 4.*
Therefore, the length of the eraser is 4 centimetres.*
Answer: 4 cm
Example 8: A blue strip of paper is 7 cm long. A red strip of paper is 10 cm long. How many centimetres longer is the red strip than the blue strip?
Solution:
Find the length of both paper strips: Red = 10 cm, Blue = 7 cm.*
To find how much longer the red strip is, subtract the smaller length from the larger length.*
Calculate the difference: 10 - 7 = 3.*
Answer: 3 cm
Example 9: Tom has a wooden toy stick that measures 5 cm. He glues another identical 5 cm toy stick directly to its end to make a single super-long stick. What is the total length of the new stick?
Solution:
Length of the first toy stick = 5 cm.*
Length of the second identical toy stick = 5 cm.*
Since they are joined end-to-end, add the lengths together.*
Calculate the sum: 5 + 5 = 10.*
Answer: 10 cm
Key Points
- A centimetre (cm) is a standard unit that is the same size everywhere.
- We use a ruler as a standard tool to find out the exact length in cm.
- When measuring with a ruler, always align the start of the object with the 0 mark.
- The numbers on a ruler increase by 1\text{ cm} at each big marking line.
- Standard units prevent confusion because the measurement values do not change from person to person.