Addition Combinations

The last few days we have worked with different addition combination strategies to help us remember our addition "facts" (as us old timers refer to them). It is important for students to have strategies to figure out problems. If a student only has their facts memorized and then later down the road forgets, how are they supposed to remember again? That is when they need to have a strategy!
Over the years we have become more comfortable with adding and subtracting numbers and therefor start learning and using strategies that work for us. So why not start getting our students to think this way, a way that took some of us until our adult years.

So addition combinations you say...
Here are the ones we worked on the last few days

These are for addition combinations up to 10+10, but later helps them when using larger numbers!

Doubles
Two numbers (addends) that are the same with an even sum.
Ex:
2+2=4
10+10=20

Near Doubles
Two addends with one addend one more (or one less depending on how you look at it) away from each other. The students uses their doubles (which they all know pretty well) to help them solve these types of combinations.
Ex:
2+2=4 (double)
2+3=5 (double +1)
or
2+1=3 (double -1)
One of the number increases or decreases by one.
You can even take this on to (doubles +/- 2)

Make 10 Combinations
This is when the two addends (numbers) sum equals 10! We love this strategy because it helps students when they start adding multiple large numbers at one time.
Ex:
1+9=10
2+8=10
3+7=10
Do you see the pattern?
A question we like to ask is:
Why is that pattern happening??

Plus 10 Combinations
Students learn these quickly but usually have a hard time explaining why. Plus Ten is when you add the number 10 to a single digit number.
10+1=11
10+2=12
A student might say that you just replace the zero with the number. So our question to them is:
Why does the number added "replace" the zero? We want them to understand that it is because of PLACE VALUE not "just because it just does" or magic! **wink**

Plus 9 Combinations
TRICKY TRICKY! is what we call this one, but it's really compensation and decomposing! Fancy words, but they will know them soon. It means taking apart a number and then giving some of it's parts to another number. This strategy is a favorite once the students get it down.
Ex:
9+6=
Well, 9 and 6 aren't the "Friendliest" of numbers. So to make this a more "Friendly" problem, it would be nice to have that 9 turn into a 10. So I'm going to decompose 6 into (5+1) and compensate (give to another number) the 1 to the 9. Now I have a new equation:
10+5=15
same as
9+ 6= 9+ (1+5) How familiar does that look???
9 + 1= 10
10 + 5 = 15


Some kids like to make it a 10 first and then subtract one after they are done with the equation. That is a great strategy, but they sometimes forget to subtract that 1 the added on after they got an answer.
Ex:
9+6
Student: 10 + 6 = 16 but I have to take away one because I added one to 9 earlier. So it's actually 15.
or
Student 9+6=15 because I took 1 away from the 6 and gave it to the 9 which made 10 and now the 6 is a 5. So 10+5=15.

OK, so that was the crash course on addition strategies for combinations up to 10+10! We hope this helps! Please let us know what we can do to help you at home with your child and our student! We are here to support you!