Year 2 - Maths
Count groups of ten and extra ones
Counting and representing the numbers 20 to 99
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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 explore the counting sequence for counting to 100 and beyond representing numbers from 20-99 in different ways including marking the position on a number line They will learn to represent 20-99 in the context of length.
Lesson Summary
You will learn to count more efficiently by grouping objects into tens and then counting the groups of tens and extra ones.
Key Notes
- Ten ones are equivalent to one ten.
- When counting larger groups, it is more efficient to group objects into tens, then count the tens and extra ones.
- We can work out how many there are by counting in ones, or by counting the groups of ten and extra ones.
Vocabulary To Learn
- Digit: A single symbol used to make a numeral.
Common Mistakes To Avoid
- Children may only think of 'ones' in terms of the extra ones after the tens have been grouped, so may fail to see 45, for example, as 45 ones as well as 4 tens and 5 ones.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Ten ones are equivalent to one ten. When counting larger groups, it is more efficient to group objects into tens, then count the tens and extra ones.
2. Use this key word in a maths sentence and explain it clearly. 'Digit'
A single symbol used to make a numeral. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Children may only think of 'ones' in terms of the extra ones after the tens have been grouped, so may fail to see 45, for example, as 45 ones as well as 4 tens and 5 ones. Correction: When objects are grouped in tens, use deliberate errors and discussion to draw attention to the total number of ones represented by the number, so children are familiar with recognising both the extra ones and the total number of ones in a number.
More Lessons In This Unit
Browse all guides in the Year 2 Maths guide library.