Adding doubles, such as 4+4 or 9+9, is one important strategy for learning addition facts. The great news about learning doubles is that there are just 10 of them to learn. Learning these 10 doubles will eventually carry over into kids' being able to add numbers like 22+22 with no problem. Knowing the doubles will also help kids learn the "doubles neighbor" facts, such as 3+4 and 7+6.

Adding doubles feels somehow easier than learning the other addition facts. Visually, their symmetry is nice to look at, and they lend themselves to rhythm and songs. The goal is to spend enough time on doubles for these addition facts to become automatic, without the need to count.

Here are a selection of activities that you can use to help children learn these special addition facts. Mix it up to reach all the learning styles.

1. Make It Visual: Picture cues are a helpful memory aid for many kids in adding doubles. Here are some examples:

• 1+1 two eyes.
• 2+2 a four leaf clover.
• 3+3 two triangles or a six-pack of soda.
• 4+4 a spider.
• 5+5 two hands.
• 6+6 an open egg carton.
• 7+7 two weeks on a calendar.
• 8+8 two spiders.
• 9+9 two tic-tac-toe boards.
• 10+10 ten fingers and ten toes.

2. Doubles Rhymes: The doubled addition facts are practically made for rhythm. You might have kids make up their own rhymes, then put them in a class book with illustrations and see how fast the class memorizes them! Use them as jump rope rhymes and watch both the fun and the learning go through the roof. Here is one that I wrote; kids like it because it is also a riddle.

1+1 is 2. My friend lives at the zoo.

2+2 is 4. He eats dinner on the floor.

3+3 is 6. He sleeps curled up on sticks.

4+4 is 8. He always wakes up late.

5+5 is 10. He's getting loud again.

6+6 is 12. He's in a tree all by himself.

7+7 is 14. He's playing and cavorting.

8+8 is 16. My buddy isn't very clean.

9+9 is 18. At dinner time he's waiting.

10 +10 is 20. He likes bananas plenty.

Can you guess who my friend is? (A monkey!)

3. Adding Doubles Hopscotch: Draw the hopscotch grid as usual, with numbers up to 10. Instead of hopping through it on one foot as usual, kids will hop twice on one foot and once on both feet, as they say, "1+1 is 2", "2+2 is 4", and so on, depending on what numbered box they are in.

To make it a bit more hopscotch-ish, kids throw the stone and play as usual-with the only difference being that they hop three times in each square and say their doubles. They will, of course, skip over the square with the stone.

4. Three in a Line: Here's a fun team activity for adding doubles. Call up 3 volunteers and stand them in a line. It is played like this:

• Child 1 says "One"
• Child 2 says "Plus one"
• Child 3 says "Is two!"
• Child 3 then runs around to Child 1's place, and all of them scoot over.
• New child 1 says "Two".
• New child 2 says "Plus two", and so on.

This way, kids are rotating and all eventually have to give the answers. The trickiest part of the game is remembering what the next number is that will be doubled, so an adult could coach the kids. As number 3 is getting into his new place, the adult could call out, "Two!"

Once kids get the hang of it, see if they can do it faster. You'll have kids begging to play this game.

5. Block Doubles: Give kids interlocking blocks (like Unifix Cubes) and lead them on a variety of exploratory activities with doubles:

• Give each child a different number card with a numeral from 1-10. Ask them to make a tower with their number, then double it. Ask kids, "What was your number? What was its double? What did you notice?" Write the results on the board.
• Write a number line on the board after kids have made their doubles stacks. Include the numbers 1-20. Have kids count their blocks and tell you what they got. Circle each number they tell you on the number line. Then ask, "What do you notice about our number line? What numbers got circled? What numbers didn't get circled? Why not?"
• Ask one child to share their double. Write its number sentence on the board, such as 3+3=6. Then tell that child to add just one block to one of the sides. One side has one more! Show how to write this: 3+4. What will the answer be? How do they know? Invite the rest of the class to add one block to their structures. Have members of the class come up and show their block structures. Write both of their addition facts on the board: the double, then its neighbor. Ex: 4+4=8, 4+5=9. Ask kids what they notice.

### Neighbors of the Doubles

The doubles make up just 10 of the first grade addition facts, but if you include "neighbors of the doubles", you add in 40 more! Doubles neighbors are the numbers that sit right next to doubles, so kids can start by adding doubles, then adjust one up or down. Ex: For the addition double 4+4, you'll have neighbor doubles 5+4, 3+4, 4+3 and 4+5.

Help kids recognize when addition facts are "next door neighbors", just one number apart from one another. The memory rule here should be,
"When numbers are neighbors, get doubles to help."