Missing Number Problems

We can use our knowledge of number relationships, number facts and inverse operations to find the missing number in a calculation.

Equations

An equation is a number sentence with an = sign.
The = sign just means one side is equal to the other.
- 3 + 6 = 10 - 1
- 3 + 6 = 9 and 10 - 1 = 9, so both sides are equal.

Missing number

Sometimes we have to work out the missing number in an equation.
This is not always the number after the = sign.
For example:
- 20 + ? = 50
- 3 + ? = 10 - 1

Number facts

We can use our knowledge to help find the missing number.
- 200 + 400 = ?
We know the number fact:
- 2 + 4 = 6
The missing number is 600.

Bar models

We can use bar models to find the missing number.
- 20 + ? = 50
We can see a relationship between 50, 20 and 30.
The missing number is 30.

Inverse operations

We can use inverse operations to find the missing number.
- 27 + ? = 38
The inverse is 38 - 27 = 11.
The missing number is 11.

1Year 3 - Number

2Year 3 - Measurement

2.1Length

2.1.1Length

2.1.2Comparing Lengths

2.1.3Add & Subtract Lengths

2.1.4Perimeter

2.2Mass

2.2.1Mass

2.2.2Comparing Masses

2.2.3Add & Subtract Masses

2.3Volume & Capacity

2.3.1Volume & Capacity

2.3.2Comparing Volumes

2.3.3Add & Subtract Volumes

2.4Money

2.4.1Money

2.4.2Counting Money

2.4.3Adding & Subtracting Money

2.5Time

2.5.1Units of Time

2.5.2Clocks

2.5.3Telling the Time

2.5.4Time of the Day

2.5.512-Hour & 24-Hour Clocks

2.5.6Measuring Time

3Year 3 - Geometry

3.1Angles

3.1.1Angles in Degrees

3.1.2Types of Angle

3.2Properties of Shapes

3.2.12D Shapes

3.2.23D Shapes

3.3Straight Lines

3.3.1Straight Lines

3.3.2Parallel & Perpendicular Lines

4Year 3 - Statistics

4.1Statistics

4.1.1Statistics

4.1.2Pictograms & Bar Charts

5Year 4 - Number

6Year 4 - Measurement

6.1Units

6.1.1Metric Measurements

6.1.2Adding & Subtracting Money

6.2Time

6.2.1Converting Units of Time

6.2.2Changing the 12-Hour Clock to the 24-Hour Clock

6.2.3Changing the 24-hour Clock to the 12-Hour Clock

7Year 4 - Geometry

7.1Properties of Shapes

7.1.1Symmetry

7.1.2Types of Triangle

7.1.3Quadrilaterals

7.2Perimeter & Area

7.2.1Perimeter

7.2.2Area

7.3Position & Direction

7.3.1Coordinates

7.3.2Translation

8Year 4 - Statistics

8.1Statistics

8.1.1Types of Data

8.1.2Pictograms & Bar Charts

8.1.3Line Graphs

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