Explain how constant difference can make written calculations more efficient
Lesson details
Learning outcome
I can explain how using the same difference rule can make written calculations easier.
Key learning points
- It is easier to use a written strategy for subtraction when no exchanging is required.
- 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.
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
Pupils may struggle to understand the purpose of transforming calculations using constant difference, especially if they are less confident in calculating using mental strategies.
Show pupils sequences of calculations with a constant difference and get them to spot which of them is easiest to complete. Start as simply as you need to here. Constant difference is a helpful tool not a new method designed to lower confidence.
Teacher tip
Even after adjustment, some of the mental maths required is tricky so change the calculations if needed or select simpler ones to establish the concept.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Match the pairs of number complements to 100
84
45
69
58
Q2.Use a mental strategy to sum these multiples of 10
560 + 120 =
Q3.Add together these multiples of 1,000 using a mental strategy.
{{ ]} = 15,000 + 27,000
Q4.Complete this subtraction using a mental strategy.
67,000 − 12,000 =
Q5.How much change would I get from £20 if I spent £11.75 on a new football? £ change.
Q6.I have a ball of old plasticine that weighs 750 g and a new jumbo pack that weight 1.2 kg. What mass of plasticine do I have altogether?
Assessment exit quiz
6 Questions
Q1.Which of the following expressions is not equivalent to the others?
Q2.Which of the following expressions is not equivalent to the others?
Q3.Match the expression with the adjustment to the minuend and subtrahend that will make them more efficient for calculation.
− 1
+ 1
− 2
+ 3
Q4.Use adjustment of the minuend and subtrahend followed by your understanding of place value.
20.58 − 5.96 =
Q5.Use adjustment of the minuend and subtrahend followed by partitioning to calculate the following subtraction.
70,559 − 54,504 =
Q6.Use adjustment followed by a written procedure to calculate the following.
40,000 − 2,654 =
To help you plan your 6 maths lesson on: Explain how constant difference can make written calculations more efficient, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 6 maths lesson on: Explain how constant difference can make written calculations more efficient, 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.