My 6-year-old granddaughter visited again in April. Besides having so much fun taking her to the zoo, Butterfly Pavilion, the movies, reading books, baking, playing outside, and doing arts & crafts, we also played a card game which required adding up points and keeping score. The cards’ values had to be added, and I was impressed that she was eager to count up both her points and mine. (I don’t think she realized she was doing mathwork.)
At one point, when she had to add 9 plus another number, I decided to show her the “Magic 9” strategy. I knew she could count it out herself, so now it was time for the strategy which would save her lots of unnecessary counting.
Magic 9:
9 + 8 and 8+9 . Look at the 9, then point to the other number, or 8 in this case. What is one less than 8? 7. The answer is 17.
9 + 7 and 7+9. Look at the 9, then point to the other number, or 7 in this case. What is one less than 7? 6. The answer is 16.
9 + 5 and 5+9. Look at the 9, then point to the other number, or 5 in this case. What is one less than 5? 4. The answer is 14.
9 + 2 and 2+9. Look at the 9, then point to the other number, or 2 in this case. What is one less than 2? 1. The answer is 11.
Magic 9 also works for 9+9, 9+6, 9+4, 9+3.
Important!
Show with counters first, and show that one less on the other number becomes one more on the 9 which equals 10. Students ought to know 10 plus a number. (10+1=11, 10+2=12, 10+3=13…)
Example: 9+4 x x x x x x x x x + x x x x
Take one x from the 4 and place it on the 9.
x x x x x x x x x x + x x x
10 + 3 = 13.
Two Plus Two Is Not Five offers lots of strategies to help children memorize addition and subtraction facts!
