1.2.5

Missing Number Problems

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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

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

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

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

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

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.
Jump to other topics
1

Year 3 - Number

1.1

Number & Place Value

1.1.1Multiples1.1.2Counting in Multiples1.1.3Recognising Three-Digit Numbers1.1.4Finding 10 More or Less than a Number1.1.5Finding 100 More or Less than a Number1.1.6Ordering & Comparing Numbers up to 1,0001.1.7Writing & Reading Numbers1.1.8Representing Numbers
1.2

Addition & Subtraction

1.2.1Mental Addition & Subtraction1.2.2Column Method1.2.3Estimating Calculations1.2.4Inverse Operations1.2.5Missing Number Problems1.2.6Real-Life Problems
1.3

Multiplication & Division

1.3.1Times Tables1.3.2Using Times Tables1.3.3Multiplying Numbers1.3.4Missing Number Problems1.3.5Real-Life Problems
1.4

Fractions

1.4.1Tenths1.4.2Fractions1.4.3Fractions Equal to a Whole1.4.4Equivalent Fractions1.4.5Fractions of Shapes1.4.6Fractions of Amounts1.4.7Add & Subtract Fractions1.4.8Compare & Order Fractions
2

Year 3 - Measurement

2.1

Length

2.1.1Length2.1.2Comparing Lengths2.1.3Add & Subtract Lengths2.1.4Perimeter
2.2

Mass

2.2.1Mass2.2.2Comparing Masses2.2.3Add & Subtract Masses
2.3

Volume & Capacity

2.3.1Volume & Capacity2.3.2Comparing Volumes2.3.3Add & Subtract Volumes
2.4

Money

2.4.1Money2.4.2Counting Money2.4.3Adding & Subtracting Money
2.5

Time

2.5.1Units of Time2.5.2Clocks2.5.3Telling the Time2.5.4Time of the Day2.5.512-Hour & 24-Hour Clocks2.5.6Measuring Time
3

Year 3 - Geometry

3.1

Angles

3.1.1Angles in Degrees3.1.2Types of Angle
3.2

Properties of Shapes

3.2.12D Shapes3.2.23D Shapes
3.3

Straight Lines

3.3.1Straight Lines3.3.2Parallel & Perpendicular Lines
4

Year 3 - Statistics

4.1

Statistics

4.1.1Statistics4.1.2Pictograms & Bar Charts
5

Year 4 - Number

5.1

Number & Place Value

5.1.1Counting in Multiples5.1.2Recognising Four Digit Numbers5.1.3Find 1,000 More or Less than a Number5.1.4Negative Numbers5.1.5Ordering & Comparing Numbers Over 1,0005.1.6Representing Numbers5.1.7Rounding Numbers5.1.8Roman Numerals
5.2

Addition & Subtraction

5.2.1Written Methods for Adding Large Numbers5.2.2Written Methods for Subtracting Large Numbers5.2.3Estimation & Inverse Operations5.2.4Solving Two-Step Problems
5.3

Multiplication & Division

5.3.1Times Tables5.3.2Using Times Tables5.3.3Multiplication Rules5.3.4Column Method5.3.5Factors
5.4

Fractions & Decimals

5.4.1Identifying Equivalent Fractions5.4.2Adding & Subtracting Fractions5.4.3Hundredths5.4.4Decimals5.4.5Converting Between Decimals & Fractions5.4.6Rounding Decimals5.4.7Ordering Decimals
6

Year 4 - Measurement

6.1

Units

6.1.1Metric Measurements6.1.2Adding & Subtracting Money
6.2

Time

6.2.1Converting Units of Time6.2.2Changing the 12-Hour Clock to the 24-Hour Clock6.2.3Changing the 24-hour Clock to the 12-Hour Clock
7

Year 4 - Geometry

7.1

Properties of Shapes

7.1.1Symmetry7.1.2Types of Triangle7.1.3Quadrilaterals
7.2

Perimeter & Area

7.2.1Perimeter7.2.2Area
7.3

Position & Direction

7.3.1Coordinates7.3.2Translation
8

Year 4 - Statistics

8.1

Statistics

8.1.1Types of Data8.1.2Pictograms & Bar Charts8.1.3Line Graphs

Practice questions on Missing Number Problems

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

  1. 1
    Using the bar model, what is the missing number? <br>35 &plus; ? = 60Multiple choice
  2. 2
    Using the bar model, what is the missing number? <br>50 &minus; ? = 40Multiple choice
  3. 3
    Using the bar model, what is the missing number? <br>20 &plus; ? = 70Multiple choice
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Inverse Operations

Real-Life Problems