Starter quiz
- Match the pairs of number complements to 100
- 34⇔66 ✓
- 12⇔88 ✓
- 43⇔57 ✓
- 54⇔46 ✓
- Use a mental strategy to sum these multiples of 100 5,300 + 1,800 = ______
- '7,100' ✓
- Add together these multiples of 1,000 using a mental strategy. ______ = 117,000 + 19,000
- '136,000' ✓
- Complete this subtraction using a mental strategy. 367,000 − 24,000 = ______
- '343,000' ✓
- How much change would I get from £20 if I spent £10.98 on a new football? £______ change.
- '9.02' ✓
- I have a ball of old plasticine that weighs 655 g and a new jumbo pack that weight 1.4 kg. What mass of plasticine do I have altogether?
- '2.055 kg' ✓
Exit quiz
- Use your understanding of constant difference to work out which of the equations in the sequence is incorrect.
- 56 − 16 = 57 − 17
- 55 − 15 = 58 − 18
- 54 − 14 = 59 − 19
- 53 − 13 = 60 − 20
- 52 − 12 = 61 − 19 ✓
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- Use your understanding of constant difference to work out which of the equations in the sequence is incorrect.
- 45 − 13 = 187 − 155
- 145 − 113 = 178 − 145 ✓
- 245 − 213 = 167 − 135
- 345 − 313 = 157 − 125
- 445 − 413 = 147 − 115
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- Use constant difference to find the unknown in the equation. 65 − ______ = 150 − 111
- '26' ✓
- Use constant difference to find the unknown in the equation. 1,510 − 1,400 = ______ − 200
- '310' ✓
- Use constant difference to find the unknown in the equation. 345,000 − 236,200 = 310,000 − ______
- '201,200' ✓
- At the gift shop on a residential week, Alex has £13.50 and Sofia has £9.20 to spend. They both buy a souvenir fridge magnet to take home. Sofia now has £6.21 left. How much does Alex have left?
- '£10.51' ✓
Worksheet
Presentation
Video
Lesson Details
Key learning points
- If I add __ to the minuend and add the same number to the subtrahend, the difference stays the same.
- If I subtract __ from the minuend and add the same number to the subtrahend, the difference stays the same.
- A number line can be used to represent the 'same difference' generalization.
Common misconception
Lots of pupils will want to calculate the value of the expression with the known parts in order to calculate the unknown part without considering a more efficient approach.
Calculating the value of one expression is efficient with simple numbers but encourage the children to try and compare the parts instead. As the numbers get harder, calculating the expression becomes much less efficient.
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.
Unknown - An unknown is a quantity that has a set value but it is represented by a symbol or letter.