Starter quiz
- Match the pairs of number complements to 100
- 23⇔77 ✓
- 34⇔66 ✓
- 91⇔9 ✓
- 58⇔42 ✓
- Use a mental strategy to sum these multiples of 10 340 + 500 = ______
- '840' ✓
- Add together these multiples of 1,000 using a mental strategy. ______ = 12,000 + 7,000
- '19,000' ✓
- Complete this subtraction using a mental strategy. 19,000 − 15,000 = ______
- '4,000' ✓
- How much change would I get from £20 if I spent £13.50 on a new football? £______ change.
- '6.50' ✓
- 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?
- '1.4 kg' ✓
Exit quiz
- What is the constant difference between all of the expressions below? 99 − 27 = 89 − 17 = 79 − 7
- '72' ✓
- Which word fills in the blank in this sentence? If the minuend and subtrahend are changed by the same amount, the difference remains __________.
- different
- constant ✓
- greater
- less
-
- What is the constant difference being shown in these expressions? 28 − 12 40 − 24 115 − 99
- '16' ✓
- What is the missing number in the equation below? 16 − 9 = 36 − ______
- '29' ✓
- 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?
- '34' ✓
- 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
- '17' ✓
Worksheet
Presentation
Video
Lesson Details
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.
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.
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.
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