Line the objects up in twos. Either they all have a partner, or one does not.
Step 1: Let's Learn
Read it, or press Listen and follow the words.
If every object has a partner, the number is even.
Even means the objects pair up with none left over.
If one object is left on its own, the number is odd.
Odd means one object is left over when you pair them up.
Not a rule about the last digit
You can check any number by pairing. You do not have to remember a rule.
The pairing test
Take a number of counters and pair them up. If every counter has a partner, the number is even. If one is left over with no partner, the number is odd. That is the whole definition, and it works for any number no matter how big.
The shortcut using the last digit
You do not need counters for large numbers. Look only at the ones digit: 0, 2, 4, 6 or 8 means even; 1, 3, 5, 7 or 9 means odd. So 346 is even and 571 is odd. The earlier digits make no difference at all, because every ten and every hundred is itself an even amount.
What happens when you add them
Even plus even is even. Odd plus odd is even — the two leftovers pair up with each other. Odd plus even is odd. Try a few and you will see it always holds. This is real mathematical reasoning: a rule you discovered from a pattern and can explain.
Step 2: Try It Yourself
Change the number and watch the leftover appear and disappear.
8 makes 4 pairs with none left over, so 8 is even.
4 + 4 = 8
Step 3: Watch an Example
One step at a time.
Watch Ana Pair Up 9
Ana has 9 counters.
- Step 1
She puts them into pairs, one pair at a time.
Step 4: Your Turn
Practice makes it stick.
Sharing Socks
Problem 1 of 2
There are 14 socks. Can every sock find a partner?
The Team
Problem 2 of 2
11 children want to work in pairs. Will anyone be left out?
Odd or Even?
1 of 3
Is 12 odd or even?
2 of 3
Is 15 odd or even?
3 of 3
How many pairs does 16 make?
Step 5: Quick Check
Show what you know.
Question 1 of 2
Is 18 odd or even?
Question 2 of 2
What does even mean?
What You Learned
- Pair the objects up to test a number.
- None left over means even.
- One left over means odd.