Mathematics

Advanced

50 mins

Teacher/Student led

Learning Goals

Learning Outcomes

Lesson Files

+80 XP

Teacher-led from the board. Pupils do not need a device, but can follow on one.

What you need:
IWB/Projector/Large Screen

Finding the Missing Number

Find missing numbers hidden in a box within number sentences by keeping both sides balanced, then check your answer by substituting the number back in.

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1 Getting Started
2 Watch and Notice
3 Try It Together
4 Solve Them in Your Copy
5 Class Challenge
6 What Did We Notice?
7 What's Next
Pupil practice

Your turn

Your teacher is running this lesson on the board. Here is the part you can try yourself.

Your written work is on page 112

Balance scales

1 - Getting Started ~4 mins

Here is a puzzle: □ + 5 = 12. The box is hiding a number. What number do you think is hiding in the box to make both sides equal?

👇 Mark your steps as done as you complete them.

+5 XP

2 - Watch and Notice ~12 mins

Watch the balance beam. A box hides a number, and the beam only stays level when the box holds the right value. To find the box, we do the opposite of what is beside it. Whisper your prediction for each beam, then check that it is level.

👇 Mark your steps as done as you complete them.

+10 XP

3 - Try It Together ~8 mins

Key point

Do the opposite of what is beside the box. For □ − 18 = 35 the box must be bigger than 35, because 18 is taken away from it.

We start on the balance beam with □ + 24 = 51. Slide the box until the beam levels, then read off what the box holds. Then we talk through the next ones together: □ − 18 = 35, then 72 = □ + 45, then 36 + □ = 90.

Find the box to level the beam

+15 XP

4 - Solve Them in Your Copy ~3 mins

COPYBOOK MOMENT

In your maths copy, solve these five sentences and write the value of the box for each one:

□ + 38 = 100
□ − 25 = 47
64 = □ + 29
□ × 6 = 42
56 ÷ □ = 8

Then check each one by writing out the whole sentence with your number in place of the box, and read it back to yourself.

+10 XP

Pupil practice

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

Lesson 121 · Finding the Missing Number

Download Activity Book page (PDF)

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