New
New
Year 2
Subtract two-digit numbers crossing the tens boundary
I can subtract two-digit numbers crossing the tens boundary.
New
New
Year 2
Subtract two-digit numbers crossing the tens boundary
I can subtract two-digit numbers crossing the tens boundary.
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Lesson details
Key learning points
- When subtracting, the known part of the whole can be partitioned further to subtract the tens and the ones separately.
- Partitioning both the whole and the parts when subtracting gives a correct answer when the ones digits bridge 10
- The tens and ones can be subtracted in any order and the remaining part will stay the same.
Keywords
Partition - To split a whole up into parts; a piece or section of a whole.
Part - A piece or section of a whole.
Common misconception
Children may spot a pattern and be able to continue it based on noticing numbers simply increasing or decreasing without making the generalisations needed to understand why this happens.
Encourage children to articulate not only the pattern, but also why it has occurred, at first using practical equipment to prove it, then mentally visualising and manipulating the numbers involved.
It is important to search for patterns when solving equations not only because it can help children to solve the next equations efficiently, but also because it helps them to make generalisations about the ways in which numbers work in different situations.
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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Starter quiz
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6 Questions
Q1.
Which bar model could represent the problem shown? There were 56 animals on the farm. 40 were sheep, 2 were pigs and the rest were cows. How many cows were there?
C
Q2.
Which number line represents what has happened in the problem? First, there were 96 children in the hall, then 1 left, then 40 more left. How many children are left in the hall now?
C
Q3.
Izzy had 78 p and spends 42 p. How much money does she have left? Use the coins shown to help you find out.
35 p
46 p
Q4.
Which number line represents what has happened in the problem? I had 74 stickers on my chart. 34 were smiley faces and rest were stars. How many were stars?
A
Q5.
Andeep counts 87 minibeasts in the garden. 35 were ants and the rest were woodlice. How many woodlice were there? Which equation would solve this problem? Tick all that apply.
87 − 3 − 5 = 79
Q6.
There are 86 crows on the farmer’s field and 53 fly away. How many crows are left? Write the equation to solve this problem.
Exit quiz
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6 Questions
Q1.
Which of the following equations will have a difference of a multiple of 10?
43 − 34 = ?
Q2.
Which number line could be used to solve the equation shown? 63 − 29 = ?
Q3.
Use the pattern to predict the answer to the next equation. 74 − 49 =
Q4.
Use the pattern to predict the next equation in the sequence.
Q5.
Write a subtraction equation, then solve it to find the missing part in the bar model.
Q6.
Match each equation to the number that correctly completes it.
38
42
58