Find 10 more or less than a 2-digit number.
I can find 10 more or 10 less than a two-digit number.
Find 10 more or less than a 2-digit number.
I can find 10 more or 10 less than a two-digit number.
Lesson details
Key learning points
- When finding 10 more or 10 less than any two-digit number, the ones digits does not change.
- When finding 10 more than a number below 100, the tens digit increases by one.
- When finding 10 less than a number below 100, the tens digit decreases by one.
Keywords
10 more - 10 more than is when there is a greater amount by 10 than another item in the set.
10 less - 10 less than is when there is a smaller value by 10
Increase - Make something bigger (in size or quantity).
Decrease - Make something smaller (in size or quantity).
Common misconception
Children may default to counting in ones to find ten more or ten less.
Use representations that highlight the structure of the base 10 system, e.g. Base 10 blocks/one hundred squares, and also 'dual counting' to support understanding of 'unitising', i.e. that using 'ten' as a unit can help to calculate more efficiently.
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
6 Questions
Exit quiz
6 Questions
40
20
90
50
100
40
50
100
60
the tens digit increases by one, but the ones digit remains the same.
the tens digit decreases by one, but the ones digit remains the same.
27
33
56
75
