New
New
Year 6

Explain and represent constant difference for subtraction

I can explain and represent constant difference for subtraction.

New
New
Year 6

Explain and represent constant difference for subtraction

I can explain and represent constant difference for subtraction.

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Lesson details

Key learning points

  1. If the minuend and subtrahend are both increased by the same amount, the difference stays the same.
  2. If the minuend and subtrahend are both decreased by the same amount, the difference stays the same.
  3. 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.

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.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), 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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6 Questions

Q1.
Match the pairs of number complements to 100
Correct Answer:23,77

77

Correct Answer:34,66

66

Correct Answer:91,9

9

Correct Answer:58,42

42

Q2.
Use a mental strategy to sum these multiples of 10 340 + 500 =
Correct Answer: 840
Q3.
Add together these multiples of 1,000 using a mental strategy. = 12,000 + 7,000
Correct Answer: 19,000
Q4.
Complete this subtraction using a mental strategy. 19,000 − 15,000 =
Correct Answer: 4,000
Q5.
How much change would I get from £20 if I spent £13.50 on a new football? £ change.
Correct Answer: 6.50, £6.50
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?
Correct Answer: 1.4 kg, 1,400 g, 1.4, 1,400

6 Questions

Q1.
What is the constant difference between all of the expressions below? 99 − 27 = 89 − 17 = 79 − 7
Correct Answer: 72
Q2.
Which word fills in the blank in this sentence? If the minuend and subtrahend are changed by the same amount, the difference remains __________.
different
Correct answer: constant
greater
less
Q3.
What is the constant difference being shown in these expressions? 28 − 12 40 − 24 115 − 99
Correct Answer: 16
Q4.
What is the missing number in the equation below? 16 − 9 = 36 −
Correct Answer: 29
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?
Correct Answer: 34
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
Correct Answer: 17