Counting to 100

In the last lesson, we thought of numbers as answers to “how many?” Now we put those numbers in order so we can count, compare, and move through them with confidence.

Try this out loud: count slowly from one to ten. You are already using order — each number is one step after the previous one.

A number line is a picture of numbers in order. We draw a straight line and spread the numbers along it. Smaller numbers sit to the left; larger numbers sit to the right.

You might first meet a short line, say from 0 to 20. The same idea stretches all the way to 100 and beyond: one hop to the right is “one more,” one hop to the left is “one less.”

Use the slider above to pick any number from 0 to 100. The boxes show “one more” and “one less” — your neighbours on the line.

For example, if you land on 47, one more is 48 and one less is 46. At the ends (0 or 100), there is no neighbour on one side, so you will see a dash.

When you count up, you add one each time: the next number is always one more than the one you just said. When you count down, you subtract one each time.

The interesting moments are when you cross a “ten boundary.” Listen to this chain: 28, 29, 30, 31. After 29, the tens digit changes — you have a full new ten. Saying it slowly helps your brain notice the pattern.

You can count down across a boundary too: 33, 32, 31, 30, 29. The same idea works anywhere on the line.

A hundred square packs the numbers 1 to 100 into a grid with ten rows and ten columns. Reading left to right along a row, each step is +1. Reading down a column, each step is +10 (a whole new row of tens).

Numbers in the same column share the same “ones” digit: 4, 14, 24, 34 … all end in four. That pattern is a clue for counting and for place value in the next lesson.

Pick a cell, then try +1 and −1 to slide along a row. Try +10 and −10 to move straight down or up. Notice how +10 lines up with “one row below” on the square.

Answer in your head or on paper, then open “Show answer” to check. There is no timer — take your time.

You can now move confidently along the number line to 100 and read patterns on a hundred square. Next, in lesson 1.1.3, we look at place value — why the position of a digit changes how much it is worth.