Here are three short patterns. Look hard at each one.

• 2, 4, 6, 8, …
• 5, 10, 15, …
• 20, 18, 16, …

What number do you think comes next in each one? And here is the real question: how did you know?

Each number line marks out a counting pattern. Watch the size of the hop from one number to the next. Is every hop the same, and which way does it go?

On screen is our hundred square — all the numbers from 1 to 100 laid out in rows. A pattern shows up on it as a path: start at a number, count on by the step, and shade every number you land on.

We will do four rounds. Each round, a starting number and a step are called out. One of you comes up and shades the pattern across the grid while the rest of us say each number as it is shaded. Then we agree the rule together — or fix it.

Today we work through these patterns together on the number line. Find the missing number or the next number each time, and be ready to say the rule:

• Continue 3, 6, 9, …
• Continue 50, 45, 40, …
• Fill the gap: 10, ?, 20, 25
• Continue 100, 90, 80, 70, and be ready to name the rule

We show every answer the same way: drag the marker to that number on the 0–100 line. The pattern lives in the question; the line is where we show the answer.

Today we learned

• Every number pattern is built by repeating the same step.
• Once you spot the step, you can say what comes next without counting every number.
• Patterns can count on (the step is added) or count back (the step is taken away).

Coming up

Next we look at growing patterns made from shapes, and how to predict a stage we have not even built yet.