Look at this pattern of tiles growing step by step: 3 tiles, then 5, then 7. It keeps growing the same way each time. We call which step we are on the term-number — so the 1st pattern is term-number 1, the 2nd is term-number 2, and so on — and we call how many tiles are in it the value. Here is the big question: how many tiles would be in term-number 10? And could you work it out without drawing all ten patterns?
Take three hands-up answers, not open call-outs. Some pupils will keep counting up the pattern (9, 11, 13...) — that's a fine starting point. Hold the 'without drawing all ten' part as the hook tension; don't resolve it yet.
Watch as we feed the term-numbers 1, 2 and 3 through the machine. Out come the values 3, 5 and 7. Look at how the values change: 3, then 5, then 7 — they go up by 2 each time. That jump of 2 is exactly what we multiply the term-number by, so the rule starts with × 2. But term-number 1 times 2 is only 2, and our first value is 3, so we need a + 1 to land on it. The rule is: take the term-number, times it by 2, then add 1.
Now a different machine. Feeding in 1, 2, 3 gives 3, 6, 9. These values go up by 3 each time, so we multiply the term-number by 3. Check the first value: term-number 1 times 3 is 3, which matches exactly, so we need no adding or taking away this time. The rule is simply the term-number times 3.
This machine gives 3, 7, 11 for 1, 2, 3. These values jump up by 4 each time, so we multiply the term-number by 4. But term-number 1 times 4 is 4, and our first value is only 3, so this time we take away 1 to land on it. The rule is the term-number times 4, then take away 1.
Walk each example aloud, one at a time, and pause between them so each rule lands before the next starts.
The key move: the jump between values tells you what to multiply by; then you adjust with a + or − to land on the first value. This bridge is now on the board for pupils to read, not only spoken.
Today we work through this together: we have a growing pattern that starts 3, 5, 7. Let's feed the next term-numbers through the machine, read off the values, and fill the table on the board. Before each one, see if you can predict the value first. Then we'll say the rule out loud: term-number times 2, plus 1.
This round is for talking it through together — pupils take turns at the board and the class agrees or corrects out loud.
Set the machine to the ×2 then +1 rule in explore mode (the rule is visible here, unlike the earlier hidden-rule work). Call a term-number, ask the class to predict the value before an individual pupil sends it through, then the class reads the value and you add the pair to the term-number/value table on the board. Rotate four pupils through terms 4, 5, 6, then jump to term 10.
Watch for: pupils who add 1 first then multiply (gives the wrong value). Revoice: 'multiply by two FIRST, then add the one.' When you reach term 10, ask the class to predict before sending it through.
In your maths copy, draw a two-row table. Label the top row 'term-number' and the bottom row 'value'. Fill in terms 1 to 5 for our pattern (3, 5, 7, then keep it going). Underneath the table, write the rule as a full sentence: 'The value is the term-number times 2, plus 1.'
Walk the room glancing at whether each table fills terms 4 and 5 correctly (9 and 11) and whether the rule sentence reads as a full sentence — this is whole-class copybook practice, not marking.
Today's challenge is a hidden-rule investigation. We have a matchstick-square pattern, and the machine knows the rule but won't tell us. Let's send a few numbers of squares through, watch the matchsticks come out, build the table together, and work out the rule for ourselves. Once we have it, we'll leap all the way to the 50th pattern without counting up.
This round is the practice bank — pupils take turns at the board, check each answer, and the class confirms before moving on. Keep the board work brisk rather than over-explaining.
The interactive holds four hidden-rule sub-challenges. In your 8 minutes, run the warm-up (×3) and the matchstick squares (×3 then +1) as the core work; treat the harder (×4 +1) and stretch (×5 −2, then leap to term 50) as stretch if time allows.
Let pupils probe a few inputs in the hidden-rule challenge, then build the rule from the picker and Check. Fast finishers wait quietly, mouth the next term, or watch the board.
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