Add two-digit numbers without crossing the tens boundary
Lesson details
Learning outcome
I can add two-digit numbers without crossing the tens boundary.
Key learning points
- Two-digit numbers can be added by using Base 10 equipment to combine the tens and the ones.
- Partitioning two-digit numbers can help when adding them.
- Either the tens or the ones can be added first, the sum will remain the same.
- Considering the number of tens when adding two-digit numbers can help estimate the sum.
Keywords
Partition - To split a whole up into parts.
Common misconception
Children may transpose digits in the numbers, so add tens as ones and vice versa. They may also use inefficient counting strategies to count on in tens, then ones.
Ensure that the numbers are partitioned into tens and ones, so their place value is clear and the link to known facts can be easily seen. Refer back to known facts using the stem sentence 'I know that..., so I know that ...'
Teacher tip
Ensure that children can confidently partition two-digit numbers into tens and ones before accessing the content of this lesson. As the concept is understood, children can be encouraged to solve the equations mentally, articulating thinking afterwards to ensure efficient methods are being used.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Use the Base 10 blocks shown to solve the equation
Q2.Match the expressions which have the same value.
3 + 1 + 50 + 20
2 + 30 + 4 + 20
2 + 40 + 50 + 4
Q3.What is the missing whole in the bar model?
Q4.Tick the equation which is correct.
Q5.What is the missing addend in the equation? 5 + ___+ 40 + 20 = 67
Q6.Which of the digit cards shown would complete the equation?
Assessment exit quiz
6 Questions
Q1.Match the expressions which will have the same value.
4 + 3 + 30 + 20
30 + 2 + 20 + 3
3 + 30 + 40 + 2
Q2.Which expression will have the same sum as 45 + 23?
Q3.Which equation will have a sum in the nineties?
Q4.Which equation will have a sum greater than 54 + 21 = ?
Q5.52 + 34 = 50 + + 30 + 4
Q6.35 + 52 = 87, so 32 + 55 =
To help you plan your 2 maths lesson on: Add two-digit numbers without crossing the tens boundary, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 2 maths lesson on: Add two-digit numbers without crossing the tens boundary, 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 1 maths lessons from the Addition and subtraction of two 2-digit numbers unit, dive into the full primary maths curriculum, or learn more about lesson planning.