New
New
Identify knowns and unknowns in subtraction equations
I can identify knowns and unknowns in subtraction equations.
Lesson 5 of 10
New
New
- Year 3
Identify knowns and unknowns in subtraction equations
I can identify knowns and unknowns in subtraction equations.
Lesson details
Key learning points
- Equations can be represented using part-part-whole or bar models.
- If the minuend is missing, you add the subtrahend and difference.
- To find a missing part in a subtraction equation, subtract the other part from the whole.
Keywords
Minuend - The minuend is the number being subtracted from.
Subtrahend - A subtrahend is a number subtracted from another.
Difference - The difference is the result after subtracting one number from another.
Common misconception
Pupils may rely on the same strategies to solve all problems and may find it hard to remember when to add to find the missing part and when to subtract.
Emphasise the use of bar models, especially for pupils who are struggling. This will help them identify whether a part is missing or if the whole is missing, and whether they should add the parts or subtract a part from the whole to get the answer.
Bar models and number lines may be useful for this session. The numbers involved should be very familiar to pupils, but they may find the concept of subtraction calculations with missing parts challenging, especially deciding when they should use addition or subtraction to find the answer.
Teacher tip
Licence
This content is © Oak National Academy Limited (2025), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Which number represents the subtrahend in this equation? 31 − 10 = 21
Which number represents the subtrahend in this equation? 31 − 10 = 21
31
21
Q2.What is the difference between 19 and 21?
What is the difference between 19 and 21?
Q3.What is 100 − 30 =
What is 100 − 30 =
Q4.What is 200 − 50 =
What is 200 − 50 =
Q5.Calculate the missing number is this equation: 40 + ___ = 220
Calculate the missing number is this equation: 40 + ___ = 220
160
170
200
Q6.Which pairs of numbers have a sum of 600?
Which pairs of numbers have a sum of 600?
100 and 400
200 and 500
Assessment exit quiz
6 Questions
Q1.Which number in this equation is the minuend? 63 = 103 − 40
Which number in this equation is the minuend? 63 = 103 − 40
40
63
Q2.What is the difference between 190 and 210?
What is the difference between 190 and 210?
Q3.Calculate the missing number in this equation: − 30 = 60
Calculate the missing number in this equation: − 30 = 60
Q4.Calculate the missing number in this equation: 63 − = 20
Calculate the missing number in this equation: 63 − = 20
Q5.Match up the differences with the correct expression to complete each equation.
Match up the differences with the correct expression to complete each equation.
Q6.Sylvie the snail creeps 130 cm towards home. She still has 105 cm to go before she gets there. How many cm will she have travelled altogether? cm
Sylvie the snail creeps 130 cm towards home. She still has 105 cm to go before she gets there. How many cm will she have travelled altogether? cm
