GoalTell whether a number is even or odd by pairing and by looking at the ones digit.
New words
even · can be shared into pairs with none left overodd · when you make pairs, one is left overpair · two things that go together
Explanation
An even number can be put into pairs with none left over. 8 is even: 4 pairs. An odd number always leaves one over. 7 is odd: 3 pairs and 1 left over. Look at the ones digit to decide, even for big numbers. A number is even if it ends in 0, 2, 4, 6 or 8. A number is odd if it ends in 1, 3, 5, 7 or 9. So 36 is even because it ends in 6, and 53 is odd because it ends in 3. On the number chart below, even numbers have one color and odd numbers have another, and they take turns: odd, even, odd, even.
Worked examples
8 stars in pairs: 4 pairs and none left over. 8 is even.
7 stars in pairs: 3 pairs and 1 left over. 7 is odd.
Number
Ones digit
Even or odd?
36
6
even
53
3
odd
Check the ones digit. 36 ends in 6, so it is even. 53 ends in 3, so it is odd.
Class activity
Pair hunt. Take 15 small things such as beans or buttons. Make pairs and see if one is left over. Then take 12 things and do it again. Try other numbers up to 20 and write each one in a list: even or odd. What do you notice about the numbers that are next to each other?
Practice
1
Is 12 even or odd?
Even, because it ends in 2.
2
Is 15 even or odd?
Odd, because it ends in 5.
3
Sort these numbers into even and odd: 4, 9, 10, 13, 20.
Even: 4, 10, 20. Odd: 9, 13.
4
Is 78 even or odd? How do you know?
Even, because it ends in 8.
5
Marwan has 9 apples and wants to share them equally with one friend. Can he?
