Year 1 - Maths
Crossing the tens boundary counting forwards
Pattern in counting from 20 to 100
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
In this unit pupils will extend their learning by counting to 100. They will explore the pattern in counting and focus on the end of the decade and the start of the new decade numbers. 
Lesson Summary
You will learn to count forwards from 1 to 100, crossing the tens boundary.
Key Notes
- The numbers from 0 to 100 have patterns that can help us to count across the tens boundary.
- They are arranged differently on a number track and on a one hundred square.
- We can count the numbers in two ways.
- When a whole number ends in a 9, it is always followed by a decade number.
Vocabulary To Learn
- Tens boundary: This is where the pattern of counting changes at the start of the number to show a new decade has started.
- Decade number: This is a multiple of 10 which marks the tens boundary where the pattern of counting changes.
Common Mistakes To Avoid
- Confusion between the number after 29, 39 etc. so saying 29,20 or twenty-none, twenty -ten.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
The numbers from 0 to 100 have patterns that can help us to count across the tens boundary. They are arranged differently on a number track and on a one hundred square.
2. Use this key word in a maths sentence and explain it clearly. 'Tens boundary'
This is where the pattern of counting changes at the start of the number to show a new decade has started. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Confusion between the number after 29, 39 etc. so saying 29,20 or twenty-none, twenty -ten. Correction: Explicitly look at the numbers that follow a number ending in 9 using stem sentence to support.
More Lessons In This Unit
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