Addition and Subtraction are important LIFE skills.
You have to know how to do both.
Remember your addition and subtraction facts should be SOLID! That means that you should know every addition and subtraction fact in a snap of a finger! Practice these at home EVERY night (including Friday, Saturday, and Sunday) for 5 minutes. I guarantee you will get faster with time.
Let's remember our fast strategies:
No paper required!
1) Counting On (use for addition)
If you are doing 4 + 7....
-First think of the largest number: 7 and count up 4 more
7..... 8, 9, 10, 11
4 + 7 = 11
2) Counting Up (use for subtraction)
If you are doing 14 - 8....
-First think of the smaller number: 8 and count up to 14
8.... 9, 10, 11, 12, 13, 14
You counted up 6 more
14 - 8 = 6
When working a paper pencil problem.
3) Regrouping: Use for both addition and subtraction
Addition Regrouping occurs when you have numbers like 28 + 17. If I add 8 ones and 7 ones, we will get 15 ones. But we do not write 15 ones, we regroup the new 10 to the tens place and keep the 5 ones. Students you can draw this out with your place value blocks.
Subtraction Regrouping
In the problem below, we were taking 32 - 17. After lining up our place values we see that there are only 2 ones. We can not take away 7 ones from 2 ones. So we need to REGROUP the tens. We had three tens, and after taking away one ten and adding it to the ones, we now twelve ones. Now you can count up from 7 to 12 and find that there are only 5 ones left.
Here is our anchor chart from class:
