Exploring Magnitude While Playing with Number Lines

 

Number lines are a great tool for helping young children develop an understanding of magnitude—the idea that numbers have a size and that numbers can be compared to one another.

Children may be able to count to 20, but that doesn't necessarily mean they understand how the numbers relate to each other. They may know that 8 comes after 7, but do they understand that 8 is close to 10? Or that 15 is farther from 10 than 12 is?

A number line can help make these relationships visible.

Start Simple

 

We can begin with a simple number line:

0 — 1 — 2 — 3 — 4 — 5 — 6 — 7 — 8 — 9 — 10

 

Rather than just using it to count, we can ask questions such as:

• “Where would 6 go?”
• “Which number is closer to 5 ... 3 or 8?”
• “What number is between 4 and 6?”
• “Where would you put 9? How do you know?”

These questions encourage children to think about the size and location of numbers, rather than just reciting the number sequence.

Estimate!

 

One of my favourite ways to use a number line is to give children a line with only the endpoints marked.

0 ____________________ 10

Ask:

“Where do you think 5 would go?”

Children have to think about where the middle of the line is.

We can then try:

0 ____________________ 20

“Where would 5 go now?”

This helps children see that the position of a number depends on the numbers at the ends of the line.

 

Use a Floor Number Line

 

A floor number line gives children the opportunity to physically experience number.

“Stand on 4. Move forward 3. Where did you land?”

We can ask children to predict where they will land before they move. This connects counting and movement with the idea that numbers have a position and a distance from one another.

Look for the Thinking

The important part isn't whether children place a number perfectly. We want to hear how they decided where it belongs.

“Why did you put it there?”

“What were you thinking about?”

“How do you know?”

Number lines give children a visual way to see that numbers aren't just a list of words we say when we count. Numbers have size, and numbers have relationships with other numbers.

Helping children develop this sense of magnitude is an important part of building strong number sense in kindergarten.

Shamrock Estimate

We invited children to examine a jar of shamrocks today and make their best estimate of how many were in the jar. We were impressed by their reasonable guesses - 54, 67, 81, etc. - as this shows they have a solid number sense. No estimate was unreasonable (0, 1 000 000). 

We used a 100 chart to help us organize the shamrocks into an accurate count since it was such a large collection. 

There were 81! The children were excited to realize their estimates were so close!

Forcing Forsythia Branches Indoors

We brought some forsythia cuttings into the classroom today and invited the children to predict how many days it will take for the blooms to open. We also asked the children to predict what colour the blooms would be - pink was the most popular guess.

Snowflake Estimation

At entry time today the children were invited to examine our guessing jar and estimate how many snowflakes were inside! One child's estimation was right on - 20 snowflakes!

Some Ontario Curriculum this activity fulfilled includes:

NS1.6 begin to use information to

estimate the number in a small set

(e.g., apply knowledge of quantity,

use a common reference such as a

five frame)