Year 2: Odd and even numbers
Part of the Year 2 multiplying and dividing chapter. Chapter overview · whole chapter on one page
Odd and even numbers
Some numbers can be made into pairs with none left over. These are even numbers. Other numbers have one left over. These are odd numbers.
4 shoes make 2 pairs with none left over, so 4 is even. 5 shoes make 2 pairs with 1 left over, so 5 is odd.
Key ideas
- Even numbers make pairs with none left over.
- Odd numbers have one left over.
- Even numbers end in 0, 2, 4, 6 or 8.
- Odd numbers end in 1, 3, 5, 7 or 9.
Key words. An even number makes pairs. An odd number has one left over.
Method. Put the things into pairs. Look for one left over.
- Make pairs. Put the 6 things into pairs.3 pairs
- Look for one left over. There is none left over.none left over
- Write the answer. A number with none left over is even.even
Check. 3 pairs make 6. 6 is even. ✓
Watch out. Odd numbers have one left over. Even numbers have none left over.
Key words. An even number makes pairs. An odd number has one left over.
Method. Put the things into pairs. Look for one left over.
- Make pairs. Put the 7 things into pairs.3 pairs
- Look for one left over. 3 pairs and 1 left over.1 left over
- Write the answer. A number with one left over is odd.odd
Check. 3 pairs make 6. 7 is odd. ✓
Watch out. Odd numbers have one left over. Even numbers have none left over.
Key words. An even number makes pairs. An odd number has one left over.
Method. Put the things into pairs. Look for one left over.
- Make pairs. Put the 14 things into pairs.7 pairs
- Look for one left over. There is none left over.none left over
- Write the answer. A number with none left over is even.even
Check. 7 pairs make 14. 14 is even. ✓
Watch out. Odd numbers have one left over. Even numbers have none left over.
Watch out
Watch out: only the last digit tells you if a number is odd or even. A number ending in 5 is odd.
Exam tip
Grown-up tip. Use socks or gloves. Ask: “Can we make pairs with none left over?” Odd and even is all about pairs.
Exercise 3E Odd and even numbers
Non-calculatorKey words. An even number makes pairs. An odd number has one left over.
Method. Put the things into pairs. Look for one left over.
- Make pairs. Put the 9 things into pairs.4 pairs
- Look for one left over. 4 pairs and 1 left over.1 left over
- Write the answer. A number with one left over is odd.odd
Check. 4 pairs make 8. 9 is odd. ✓
Watch out. Odd numbers have one left over. Even numbers have none left over.
Key words. An even number makes pairs. An odd number has one left over.
Method. Put the things into pairs. Look for one left over.
- Make pairs. Put the 10 things into pairs.5 pairs
- Look for one left over. There is none left over.none left over
- Write the answer. A number with none left over is even.even
Check. 5 pairs make 10. 10 is even. ✓
Watch out. Odd numbers have one left over. Even numbers have none left over.
Key words. An even number makes pairs. An odd number has one left over.
Method. Put the things into pairs. Look for one left over.
- Make pairs. Put the 13 things into pairs.6 pairs
- Look for one left over. 6 pairs and 1 left over.1 left over
- Write the answer. A number with one left over is odd.odd
Check. 6 pairs make 12. 13 is odd. ✓
Watch out. Odd numbers have one left over. Even numbers have none left over.
Key words. An even number makes pairs. An odd number has one left over.
Method. Put the things into pairs. Look for one left over.
- Make pairs. Put the 18 things into pairs.9 pairs
- Look for one left over. There is none left over.none left over
- Write the answer. A number with none left over is even.even
Check. 9 pairs make 18. 18 is even. ✓
Watch out. Odd numbers have one left over. Even numbers have none left over.
Method. Count the balls in each group. Make pairs. Look for one left over.
- Look at 7 balls. 7 balls make 3 pairs and 1 left over.7 is odd
- Look at 12 balls. 12 balls make 6 pairs with none left over.12 is even
- Write the answer. The even number is 12.12
Check. 6 pairs make 12, with none left over. ✓
Watch out. Look for the group that makes pairs with none left over.
Method. Look for one left over when you make pairs.
- Look at 8. 8 makes 4 pairs, with none left over. 8 is even.8 is even
- Look at 11. 11 makes 5 pairs and 1 left over. 11 is odd.11 is odd
- Look at 16 and 21. 16 makes 8 pairs. 21 makes 10 pairs and 1 left over.16 is even, 21 is odd
- Write the answer. The odd numbers are 11 and 21.11, 21
Check. 11 and 21 each have one left over when they make pairs. ✓
Watch out. The odd numbers all end in 1, 3, 5, 7 or 9.
Method. Make pairs of the children. Check for any child left out.
- Make pairs. Put the 12 children into pairs.6 pairs
- Look for any left over. No child is left out.none left over
- Write the answer. With none left over, all the children can make pairs.Yes. 12 is even.
Check. 6 pairs make 12 children. ✓
Watch out. Even numbers make pairs with none left over.
Method. Make as many pairs as you can. Count what is left over.
- Make pairs. 15 cubes make 7 pairs.7 pairs use 14 cubes
- Count what is left. Take 14 away from 15. One cube is left.15 − 14 = 1
- Write the answer. One cube is left over, so 15 is odd.1
Check. 7 pairs make 14, and 14 + 1 = 15. ✓
Watch out. The number left over tells you if the number is odd.
Method. Share the sweets into 2 equal groups. Check that none are left over.
- Share the sweets. Each friend gets 10 sweets.20 ÷ 2 = 10
- Check for any left over. There are none left over.10 + 10 = 20
- Write the answer. The sweets can be shared equally.Yes. 10 + 10 = 20.
Check. Each friend has 10, and 10 + 10 = 20. ✓
Watch out. An even number can always be shared into 2 equal groups.
Method. Test an even number. Look at its last digit.
- Test an even number. Take 4. Make pairs: 2 pairs with none left over.4 = 2 pairs
- Look at the last digit. 4 ends in 4, not 0.4 is even
- Write the answer. Even numbers can end in 0, 2, 4, 6 or 8.No. 4 is even, but it ends in 4.
Check. Make 4 into 2 pairs. None are left over. ✓
Watch out. Even numbers do not all end in 0.