Lesson 1.1.2

Counting to 100

Warm-up — we already count

Numbers answer "how many?" Lining them up in order lets you count, compare, and step forward or back with confidence.

Count slowly from one to ten out loud: each number is one step after the one before. That is order at work.

The number line

A number line is a picture of numbers in order. Draw a straight line and place the numbers along it — smaller to the left, larger to the right.

You might start with a short stretch, say from $0$ to $20$ . The same idea reaches $100$ and beyond: one step to the right is one more, one step to the left is one less.

Move along the line from 0 to 100

Your number: 47
One more: 48
One less: 46

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

For example, at $47$ , one more is $48$ and one less is $46$ . At $0$ or $100$ , there is no neighbour on one side, so you will see a dash.

Counting forward and back

Counting up means adding one each time: the next number is always one more. Counting down means subtracting one each time.

Listen for ten boundaries: $28$ , $29$ , $30$ , $31$ . After $29$ , the tens digit changes — you start a new ten. Saying the chain slowly helps you notice the pattern.

You can count down across a boundary too: $33$ , $32$ , $31$ , $30$ , $29$ .

The hundred square

A hundred square fits the numbers $1$ to $100$ in a grid: ten rows and ten columns. Along a row, each step is $+1$ . Down a column, each step is $+10$ .

Numbers in the same column share the same ones digit: $4$ , $14$ , $24$ , $34$ , and so on. That pattern helps with counting and sets up place value in the next lesson.

Tap a number to select it. Use the steps to see how +1, −1, and ±10 move you on the grid. Moving down one row adds 10; moving up subtracts 10.

Selected: 34 (row 4, column 4)

Pick a cell, then try $+1$ and $-1$ to move along a row, and $+10$ and $-10$ to move down or up a column.

Try it

Answer in your head or on paper, then open "Show answer" to check.

What number comes after $59$ ?
Show answer
$60$ . Counting up one from $59$ crosses into the next ten.
What is one less than $70$ ?
Show answer
$69$ . One step left on the number line from $70$ lands on $69$ .
You are counting up from $28$ . What are the next three numbers?
Show answer
$29$ , then $30$ , then $31$ . After $29$ you start a new ten.
On the hundred square, start at $34$ . Add $10$ three times in a row. Where do you finish?
Show answer
$64$ . Each $+ 10$ moves you down one row: $34$ → $44$ → $54$ → $64$ .
What whole number is between $45$ and $47$ ?
Show answer
$46$ . It is one more than $45$ and one less than $47$ .

Repeatable practice

1. $Which number is ten more than 67?$
Choose one answer687757
2. $On a hundred square you are on 63. You move one step up on the same column. Where do you land?$
Choose one answer646253
3. $What is one less than 22?$
Your answer

What is next?

Lesson 1.1.3 is about place value — why a digit's position changes how much it is worth.