• Category: 2 Ladder, addition and subtraction, addition and subtraction facts, Count by 2s, Doubles in addition, learning addition, learning math facts, math facts, strategies, Strategies to teach addition facts, subtraction, tips to teach math facts, Two Plus Two Is Not Five, using doubles addition
• Published Dated: September 12, 2014
• Written by: Susan

I currently am working with a 4th grader who has a good grasp of math skills, but came to me for help to learn to memorize math facts. I tested her to find out which facts she already knew, and began teaching her the ones she didn’t know. We are using Two Plus Two Is Not Five.

She loved learning Magic 9, which is adding 9 with any of the other numbers from 2 to 9. (9+2, 2+9, 9+3, 3+9, etc up to 8+9, 9+8, and 9+9) FIRST, I show how to take one off of the other number and adding it to the 9 to make it TEN and adding 10 + that number.
For example: 9 + 6. Take 1 off of the 6 and place it on the 9 which makes it 10. The remaining 5 +10 = 15.
I then show a very easy way to get the answers to the facts without using fingers. Magic 9: 9 + 6. Circle the 9, or just say Magic 9. Write one less than 6, which is 5. Stick a 1 in front, and you have 15. That 1 in the front is the TEN.

See previous posts for more details on how Magic 9 and the other strategies work.

Curvy Numbers (3+5, 5+3, 8+5, 5+8, 13-5, 13-8, 8-5, 8-3) was a huge help to her. On the day I introduced it, she said she had been having trouble with subtracting 13-5 and 13-8 in school, so she was glad to learn this visual strategy! Notice all the 3s, 5s, 8s?

Although she knew 3+6 and 6+3, she didn’t know 9-3 and 9-6 without counting. I taught this in a little singsong rhyme: 3,6,9 who do you think is mighty fine? (The Count by 3s will also apply in multiplication for 3×3 and 3×6 and 6×3.)

She had already known 2+4, 6+2, and 2+8, but didn’t know the subtraction facts. Once she was comfortable counting by 2s up and then down, I taught her 10-2, 8-2, 6-2.

(Count by 2 or 2 Ladder: 2,4,6,8,10  and then going backwards 10,8,6,4,2)

Being able to count backwards by 2 from 10 enabled her to think about what number is 2 less starting from 10.

Another strategy she was introduced to is Number in the Middle which is based on a student’s knowledge of the Doubles addition facts. First I introduce a worksheet to make sure they can identify what number fits in the middle, or in between two numbers.  5____7       6____8       5_____3      4_____6   8______6
This is very much a sequencing activity. She actually surprised me because she had difficulty with this task. We worked on this concept before moving on to introducing the strategy with the math facts. As mentioned, students need to first know doubles: 4+4, 5+5, 6+6, 7+7, 8+8.

Show your students a row of 6 (Unifix) cubes and a row of 8 cubes. Ask them to remove one from the 8 and place it on the 6. Ask them to say how many there are in each row. There are 7 in each row, and they will know 7+7 is 14, therefore, now they will know 6+8 and 8+6.
This wonderful strategy works for 3+5, 5+3 (which are also Curvy Number facts) 4+6, 6+4, 5+7, and 7+5.

If you find that these strategies help your students, spread the word to other teachers!