Practice

Think About It!

Goal: Remember addition doubles facts to use the doubles subtraction strategy.

If we want to help Mia the Astronaut take off to Mars, we need to help her subtract to find out how many lights are still blinking. We need to show that we are taking away the lights that went off. Let’s show that with x’s! Click each light that is off to show they are being taken away.

Now we can write a subtraction sentence to help us find the difference, or the number of lights that are still blinking. Remember, when we write a subtraction sentence it should be:

Let’s write our subtraction sentence using the questions below:

8 - 4 = ___. Where have we seen those numbers before? We know that 4 + 4 = 8. That’s a doubles addition fact! We also know that we can use our doubles facts to help us subtract. This is the doubles subtraction strategy! If we know a doubles addition fact, we have the parts and the whole! Then, we can use them to write a subtraction sentence. Click the addition sentence below to see it change into a subtraction sentence!

Now that we have discussed subtraction strategies, why don’t we make a toolbox to help us remember the tools and strategies we can use to subtract!

Let’s include counting back, since we used that in a previous lesson. We have also worked on making subtraction pictures, so let’s include a pencil, too! We can still use all of the same manipulatives that we did before; we will just be taking away instead of adding on.

Now we can help Mia find the difference of her subtraction sentence. Can you type the difference in the box below?

Today, we will focus on the doubles strategy for subtraction. Do you remember your doubles addition facts? You can use the flashcard game below as a review! After you have gotten the answer to the card click on the remove button to remove the card from the deck.