Mathematics
Intermediate
50 mins
Teacher/Student led
+95 XP
What you need:
IWB/Projector/Large Screen
Sequences and Number Lines sheet

Continuing a Pattern: What Comes Next?

Discover the hidden rule that connects each term in a sequence to the next. Watch patterns unfold, spot the pattern rule, and continue the sequence using addition, subtraction, multiplication, or a combination of steps.

Teacher Class Feed

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    1 - Getting Started ~4 mins

    Look at this row of numbers: 2, 5, 8, 11. Each number in the row is called a term: 2 is the first term, 5 is the second term, and so on. Something is happening as we move from one term to the next. What do you think comes after 11?

    Tip

    Think first, then hands up. What is the same each time you step from one term to the next?

    2 - Watch and Notice ~10 mins

    A function machine takes a number in, does the same rule to it every time, and sends a new number out. Watch what each machine does.

    Add 3 each time: 2, 5, 8, 11

    Watch the machine take 2 and turn it into 5, then 5 into 8, then 8 into 11. The same thing happens every step. What is the machine doing to each number?

    Double each time: 1, 2, 4, 8

    This machine works differently. Watch how each number doubles to make the next one. The jumps get bigger and bigger.

    Take 5 each time: 50, 45, 40, 35

    This machine goes the other way. Each number gets smaller by the same amount. What comes after 35?

    Double then add 1: 1, 3, 7, 15

    This last machine does two things to each number. Let's follow one step on screen: take 7, double it to make 14, then add 1 to make 15. So the rule is double, then add 1. Can you see both steps?

    3 - Try It Together ~8 mins

    Now we explore a hidden-rule machine together on the board. A number goes in, a different number comes out, and the same rule works every time.

    Tip

    Someone picks a number to put in. Before we press it through, the class predicts the number that will come out and says why. Then we reveal it and check.

    Hidden-rule machine

    4 - Write the Rule in Your Copy ~4 mins

    COPYBOOK MOMENT

    In your maths copy, write each of these sequences' first three terms and continue each one for two more terms. Underneath each sequence, write the rule you spotted in words.

    • 2, 5, 8, 11 … (rule: add 3 each time)
    • 1, 2, 4, 8
    • 50, 45, 40, 35

    5 - Try a Two-step Machine Together ~6 mins

    Now we try a machine that does two things to each number, just like the 'double then add 1' machine we watched.

    Someone puts a number in. Before we reveal the answer, the class works out both steps out loud: first the doubling, then the adding. Then we check the machine agrees with us.

    A two-step machine

    6 - Class Challenge ~10 mins

    Now we work through these hidden-rule machines together. Each one keeps its rule secret. We probe a few inputs, work out the rule, then check it on the next number.

    Watch out

    The last machine uses two steps, so look carefully — it does more than one thing to each number.

    Guess the hidden rule

    7 - What Did We Notice? ~3 mins

    MATHS TALK

    How do you check whether your rule is the right one? One pupil says a rule works if it fits the very last number. Another says you have to test it on every number. Who is right, and how would you settle it?

    8 - What's Next ~3 mins

    What we did today

    • Every pattern has a rule that takes you from one term to the next.
    • Some rules use one step (add 3); some use two steps (double then add 1).
    • A good rule works for the whole sequence, not just the last number.

    Coming up

    Next we will get better at putting a rule into clear words — naming both the action and the amount — so that someone else can use your rule to continue the pattern without any help.

    Pupil practice
    Module 8 · Algebra: Patterns, Expressions and Equations Algebra
    Lesson 101 · Continuing a Pattern: What Comes Next?
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