Add two-digit numbers without crossing the tens boundary
I can add two-digit numbers without crossing the tens boundary.
Add two-digit numbers without crossing the tens boundary
I can add two-digit numbers without crossing the tens boundary.
Lesson details
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.
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 ...'
Keywords
Partition - To split a whole up into parts.
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).
Video
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Starter quiz
6 Questions
3 + 1 + 50 + 20
2 + 30 + 4 + 20
2 + 40 + 50 + 4
Exit quiz
6 Questions
4 + 3 + 30 + 20
30 + 2 + 20 + 3
3 + 30 + 40 + 2