Explain and represent constant difference for subtraction
Lesson details
Learning outcome
I can explain and represent constant difference for subtraction.
Key learning points
- If the minuend and subtrahend are both increased by the same amount, the difference stays the same.
- If the minuend and subtrahend are both decreased by the same amount, the difference stays the same.
- A number line can be used to represent the 'same difference' generalisation.
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.
Constant - A constant is a quantity that has a fixed value that does not change or vary, such as a number.
Common misconception
The concept of constant difference is difficult to understand when looking simply at abstract equations and numerals and pupils may find it challenging to 'see' the underlying structure of the maths.
Make good use of physical resources to reinforce the idea of constant difference. Number rods coupled with rulers or number lines can be very useful here. Take time with smaller values so pupils can generalise.
Teacher tip
Carefully model the sequences of equations with missing numbers. You might want to start with simpler versions or get the children to create some by asking all the children to create their own expression with a given difference.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Match the pairs of number complements to 100
77
66
9
42
Q2.Use a mental strategy to sum these multiples of 10
340 + 500 =
Q3.Add together these multiples of 1,000 using a mental strategy.
= 12,000 + 7,000
Q4.Complete this subtraction using a mental strategy.
19,000 − 15,000 =
Q5.How much change would I get from £20 if I spent £13.50 on a new football? £ change.
Q6.I have a ball of old plasticine that weighs 400 g and a new jumbo pack that weighs 1 kg. What mass of plasticine do I have altogether?
Assessment exit quiz
6 Questions
Q1.What is the constant difference between all of the expressions below?
99 − 27 = 89 − 17 = 79 − 7
Q2.Which word fills in the blank in this sentence?
If the minuend and subtrahend are changed by the same amount, the difference remains __________.
Q3.What is the constant difference being shown in these expressions? 28 − 12 40 − 24 115 − 99
Q4.What is the missing number in the equation below?
16 − 9 = 36 −
Q5.Sam has 34 more flying robots than aqua robots. Sam gives away 12 flying robots and 12 aqua robots.
How many more more flying robots than aqua robots does Sam have now?
Q6.Jacob and Sam have a go at archery. Jacob scores 18 points and Sam scores 35 points. They have a second go and both score 25 more. By how many points has Sam won? points
To help you plan your 6 maths lesson on: Explain and represent constant difference for subtraction, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 6 maths lesson on: Explain and represent constant difference for subtraction, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 2 maths lessons from the Use equivalence and compensation to simplify and solve subtraction problems unit, dive into the full primary maths curriculum, or learn more about lesson planning.