Life is a series of give and take and in math class, this is also true. We give and take when we work with addition and subtraction and it is important that we learn how to do this well in order to be able to apply skills to real life situations.
Last week I focused on addition strategies for basic facts. Today I would like to look at subtraction strategies. You may notice there are many similarities between the two.
As with addition, I recommend starting with manipulatives such as base ten blocks, number lines, ten frames. These visuals will help the strategies make sense for many children.
Deciding what strategy to use will be different for each person, but in order to be able to choose, it is important to be introduced to a variety of strategies and have opportunities to practice them. Here are 6 strategies you might find helpful.
Just like in addition, zero is a special number for subtraction. Zero can be subtracted from a number and leave the same number or it can be the answer when a number is subtracted from the same number. When kids see a zero they should be able to automatically recognize this fact. It will come in very handy when they start to use larger numbers.
If you have a ruler or a number line, you can use a counting back strategy to figure out the subtraction question for basic facts. It is possible to do it for larger numbers as well, but it is not a very efficient strategy for subtracting double digit numbers.
Place your finger on the first number and count back the number of spaces of the second number to get your answer. If you use a pencil and paper with a number line, you can actually draw the steps backward. This will help to avoid getting lost or miscounting.
Related facts help when you know one fact and need to figure out the other fact. When you look at the question, think about the related fact to figure out the answer. Sometimes it is easier for us to figure out the related fact and then solve the question. It's just the way our brain works sometimes.
If you are taking away an amount that doubles to equal the first number of the subtraction question, then the answer will be the same as the amount taken away. This strategy depends on how well one knows the doubles facts.
Looking For Tens
With basic facts, tens can be a useful strategy. For instance, if you know the different combinations of numbers that equal ten, you can use fact family triangles or number bonds to figure out the different subtraction questions. If you are subtracting using a ten frame, colored objects or circles help you to see how many are remaining. See the image below as an example. For larger numbers up to 20, you could use a couple of ten frames.
Change To Addition
Sometimes it's easier to think of the question in addition rather than subtraction. You can also apply addition strategies to this. For instance, in the example below you could use doubles plus one to figure it out, or you could count on to get the answer.
Once the basic subtraction facts are well practiced, moving on to double digit subtraction and more complex questions requiring regrouping will make more sense.
Next time I will talk more about double digit addition and subtraction and strategies that will help these make sense.
About Me Charlene Sequeira
I am a wife, mother of 4, grandmother of 9, and a retired primary and music teacher. I love working with kids and continue to volunteer at school and teach ukulele.