Even and odd numbers
📖 In short
If the pupils in a class line up in twos, is anyone left on their own? If nobody is, the number is “even”; if one is, the number is “odd”. Every number is either even or odd, and the ones digit tells us quickly.
🤩 Did you know?
- Zero is an even number, because 0 ÷ 2 = 0 with nothing left over.
- Half of all numbers are even and half are odd: from 1 to 10 there are 5 even and 5 odd numbers.
- In many streets the houses with even numbers are on one side and the odd ones on the other.
- The first 3 odd numbers add up to 1 + 3 + 5 = 9, which is 3 × 3.
🔎 Find out more
🌟 Pairs
An even number splits into pairs with nothing left: 6 = three pairs. An odd number has one left after the pairs: 7 = three pairs and one. That's why we say an even number can be divided by 2.
🔍 The ones digit trick
We don't need to divide the whole number! We just look at its ones digit: if it's 0, 2, 4, 6 or 8 the number is even, and if it's 1, 3, 5, 7 or 9 it's odd. The number 3578 is even because its ones digit is 8.
💡 They always take turns
On the number line it goes even, odd, even, odd, without stopping: 1 odd, 2 even, 3 odd, 4 even… And zero is an even number.
🎯 Adding rules
Even + even = even, odd + odd = even, and even + odd = odd. Try it: 3 + 5 = 8 is even, and 4 + 3 = 7 is odd.
🧮 Worked examples
- 14 = 7 + 714 is even: it splits into two equal halves.
- 15 = 7 + 7 + 115 is odd: one is left over.
- 5 + 7 = 12Odd + odd = even.
📚 Key words
- Even number
- A number that divides by 2 with nothing left, ending in 0, 2, 4, 6 or 8
- Odd number
- A number that has one left over when divided by 2
- Remainder
- What's left after dividing that isn't enough for a whole group
🧪 Try it at home
Gather the socks in your drawer: is the number even or odd? If it's odd, one sock has lost its partner! Go and find it.
🧩 Test yourself
1 Is 47 even or odd?
2 What do you get when you add two odd numbers?
3 Which of these numbers is even?