We have been working SO hard on different subtraction strategies. There are three subtraction rules that we have learned in class.
When we have a double or triple digit algorithm where we need to subtract, we first look at the ones place.
If the 2 numbers in the ones place are the same- then zero is the game! We have learned that we just write a zero, and then go right on to the tens place.
If the number on the top of the algorithm is bigger than the bottom number, we have learned the rule “More on the top- no need to stop!” We can just subtract!
If the number on the top of the algorithm is smaller than the bottom huber, we have learned the rule “More on the floor? Go next door, get ten more”
Here is a pdf that will show you these three rules (This would be great to print and use as a reference while doing homework) subtraction strategies
Last week I noticed we were struggling with subtracting across zeros (like 100-24). So I came up with one more subtraction rule that should help us. This rule only applies if you have to borrow, or go next door to get ten more. “When you go next door and a zero is in the way, box all the tens and take one of them away.” Our kids did SO great today in class using this strategy! We are experts at boxing those tens!!! Now we just need to work on using these strategies at the correct times.
Here is a pdf that will help you understand this rule more: box the tens
Tomorrow we take our end of module test and then we move on to subtracting bigger and better numbers! 🙂