Even and Odd Numbers: Pair Them Up (2nd Grade)

What is it?

An even number of things can be split into pairs with nothing left over. An odd number always leaves one thing without a partner. Pairing is the idea behind even and odd, and it is the way 2nd graders first meet it: they circle pairs in a group of objects, then count the pairs. Later it turns into a quick rule: only the ones digit matters, so a number is even if it ends in 0, 2, 4, 6 or 8.

Step by step: 13 is odd

1. Draw 13 dots in a messy group.
2. Circle the dots two at a time. Each circle is one pair.
3. There are 6 pairs, which uses 12 dots.
4. 1 dot is left over and has no partner. A leftover means the number is odd.
5. Compare 12 dots: 6 pairs and nothing left, so 12 is even.
6. The shortcut: look at the ones digit. 13 ends in 3, and 3 is an odd digit, so 13 is odd.

Common mistakes

• Counting the pairs and stopping, without checking for a leftover dot.
• Calling a number even because it is big, or odd because it is small. Size does not matter.
• Looking at the tens digit. In 32 the 3 is odd but the number is even. Only the ones digit counts.

Your turn

Here is a problem to try. Pause and let your child work it out before you check.

Is 18 even or odd?

Answer: Even. 18 dots make 9 pairs with nothing left over. The ones digit, 8, is an even digit too.

Practice at home

Grab a handful of coins, buttons or cereal and ask your child to pair them up. Say "even" if every one has a partner and "odd" if one is left out. Then add one more and ask what changed. Next, say a number out loud and have your child guess before pairing to check.