Mathematics

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50 mins

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Writing and Solving Number Sentences with a Missing Number

You will rewrite short stories as number sentences, choosing the correct sign and placing a box for the missing number. Then you'll solve the sentence and check your answer by reading the story back with your number in place.

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1 Getting Started
2 Watch and Notice
3 Try It Together
4 Write the Sentence in Your Copy
5 Class Challenge
Pupil practice

1 - Getting Started ~4 mins

Illustration for Getting Started Listen to this short story: Aoife had some stickers. Her nan gave her 4 more, and now she has 11.

Hands up: what number sentence with a box could match this story? Where does the box go, and which sign belongs in the middle?

Teacher Notes

Read the story once, then give five seconds of quiet think-time before any hands go up. Take two or three hands-up answers, not open call-outs.

Listen for whether pupils put the box at the start (⬜ + 4 = 11) rather than reflexively at the end. Do not settle it yet — this is the exact question the lesson unpicks, and the first Watch and Notice card returns to it.

👇 Mark your steps as done as you complete them.

+5 XP

2 - Watch and Notice ~9 mins

Watch how we turn one story into a number sentence with a box, then notice the same moves in four more stories.

Worked example: Liam had 12 stickers. He gave some to his sister and had 7 left.

1. Spot the action words: gave some and had left mean take-away, so the sign is minus.

2. Ask what the story is missing: we know the start (12) and the end (7), but not how many he gave, so the box goes in the middle: 12 − ⬜ = 7.

3. Solve: what do we take from 12 to leave 7? The box is 5.

4. Read it back as a full sentence: Liam gave his sister 5 stickers.

Now look at each story below. For every one, name where the box sits (start, middle, or end) and which action words chose the sign.

Teacher Notes

Teach the Liam example on the board first, end to end, before the four stories. Stress step 2: what the story is missing decides the box place, not habit.

Story 1 (start) — Aoife had some stickers; nan gave her 4; now she has 11. Action: gave her more → plus. Missing the start → ⬜ + 4 = 11. Box = 7. Linger: work back from 11 by taking off 4.
Story 2 (middle) — same shape as Liam: There were 15 fans; some went home; 8 are left. Action: went home / left → minus. Missing the middle → 15 − ⬜ = 8. Box = 7.
Story 3 (end) — A basket had 5 apples; 7 more were added; how many now? Action: added / how many now → plus. Missing the result → 5 + 7 = ⬜. Box = 12.
Story 4 (end, change) — A bun costs 6 euro; change from a 10 euro note. Action: costs / change from → minus. Missing the result → 10 − 6 = ⬜. Box = 4.

Point pupils should reach: the box does not always go at the end; start and middle are the ones to dwell on. Slip to watch: pupils still parking the box last out of habit, or picking plus because the numbers feel like a total. If the interactive is on display, use it only to confirm each finished sentence, not as the live teach.

👇 Mark your steps as done as you complete them.

+10 XP

3 - Try It Together ~8 mins

Today we work through one missing-number sentence on the balance beam together. First we write the sentence from the story. Then we slide the unknown until both pans are level.

The story: A shelf held some tins and 3 more were added, making 9. What sentence matches it, and what must the box be to make the beam balance?

Find the box that levels the beam

Teacher Notes

Talk this one through together. Pupils take turns at the board and the class agrees or corrects out loud.

Set the sentence up as a story first, then slide the unknown. This one is ⬜ + 3 = 9, where the box comes first. Ask each pupil to read the whole sentence back with their number in the box to check.

Watch for pupils reaching for the largest number for the box out of habit. Revoice a strong answer: so we slid it until the two pans matched, and that told us the box.

+15 XP

4 - Write the Sentence in Your Copy ~3 mins

COPYBOOK MOMENT

In your maths copy, turn the two short stories your teacher reads into number sentences with a box. Solve each one, then write the answer in a full sentence (for example, "Aoife started with 7 stickers").

Teacher Notes

Read each story twice, slowly. Walk the room glancing at whether the box is in the right place and whether the sign matches the story — this is whole-class copybook practice, not marking.

Suggested stories: (1) A jar had some sweets; 5 were eaten, leaving 8. (2) A shelf had some books; 6 more were added to reach 14.

+10 XP

5 - Class Challenge ~8 mins

Now we write and solve the number sentence for four stories. For each one, name the sign, then type the answer and press Check.

A basket had 5 apples and 7 more were added. How many now?
There were 16 fans; 7 went home. How many are left?
A bun costs 6 euro — how much change from a 10 euro note?
There were 18 buns on a tray; 9 were sold. How many are left?

Write and solve the sentence

Teacher Notes

This is the practice round. Pupils take turns at the board, name the sign before pressing Check, and the class confirms before moving on. Keep the board work brisk rather than over-explaining.

The first is a joining story (add, box at the end). The second and fourth are take-aways (subtract). The third is a change story: take the price from the note.

+15 XP

Pupil practice

Module 10 · Algebra: Patterns, Rules and Number Sentences Mixed

Lesson 123 · Writing and Solving Number Sentences with a Missing Number

Download Activity Book page (PDF)

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Writing and Solving Number Sentences with a Missing Number

Teacher Class Feed

1 - Getting Started ~4 mins

2 - Watch and Notice ~9 mins

3 - Try It Together ~8 mins

Find the box that levels the beam

4 - Write the Sentence in Your Copy ~3 mins

5 - Class Challenge ~8 mins

Write and solve the sentence

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