Numbers up to 100 and Place Value: Class 2 Study Guide
Every two-digit number has tens and ones. Understanding this makes addition and subtraction much easier.
Class 2 children work with numbers up to 100 and begin to see how our number system works. In the number 64, the digit 6 is in the tens place and means 60, and the digit 4 is in the ones place and means 4. So 64 = 60 + 4.
A hundred chart or a bead frame (abacus) is useful. On an abacus, each ten is one bead on a rod, so 3 tens and 4 ones is three beads on the tens rod and four on the ones rod.
Tens and ones
| Number | Tens | Ones | Number name |
|---|---|---|---|
| 27 | 2 | 7 | twenty-seven |
| 50 | 5 | 0 | fifty |
| 84 | 8 | 4 | eighty-four |
| 99 | 9 | 9 | ninety-nine |
Counting patterns
Counting by 10s from any number keeps the ones digit the same: 7, 17, 27, 37. Counting by 5s ends in 0 or 5, and counting by 2s gives only even numbers (2, 4, 6, 8, 0). These patterns prepare children for tables and for finding odd and even numbers. An even number can be shared into two equal groups; an odd number leaves one over.
Comparing and ordering
Compare the tens first. 78 is greater than 69 because 7 tens is greater than 6 tens. If the tens are the same, compare the ones. To put numbers in order from smallest (ascending) to biggest, compare them in pairs. Greatest and smallest can be found the same way.
Which number has more tens?
Which has more ones?
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Worked examples and common mistakes
Example: Write 5 tens and 3 ones as a number: 53. Example: Which is smaller, 45 or 54? 45. Common mistakes: reversing digits, saying 'twenty-twelve', and writing 3 tens and 8 ones as 38 but 8 tens and 3 ones also as 38. Use bundles of sticks to check.
Check your understanding: model answers
1. 74. 2. 61, because 6 tens is more than 1 ten. 3. 35, 40, 45, 50, 55, 60.
✨ Key Takeaways
- A two-digit number has tens and ones.
- Count in 10s, 5s and 2s to see patterns.
- Compare the tens first, then the ones.
- Use sticks, beads or a hundred chart.
💬 Questions for Discussion & Reflection
- Write 7 tens and 4 ones as a number.
- Which is greater: 61 or 16?
- Count by 5s from 35 to 60.