Students will estimate the number of gummy worms in the jar.

In this task, students will explore the concept of quantity through estimation using their spatial reasoning skills.

Watch the full video walk-thru below to get a sense of how you might deliver this task:

Show students this video:

Then, ask students:

What do you notice?

What do you wonder?

Give students 60 seconds (or more) to do a rapid write on a piece of paper.

Then, ask students to share with their neighbours for another 60 seconds.

Finally, allow students to share with the entire group.

Some of the noticing and wondering that came up in a class recently included:

• Jar is half full.
• How many gummy worms are there?
• There are at least two different kinds of gummy worms in the jar.
• Are the gummy worms full or cut in half?
• There are two large rectangles and 4 squares along the bottom wall
• What does the tag say?
• How large is the jar?
• What kind of activity are we doing?
• Will we get some gummy worms to eat?
• and many more…

At this point, you can answer any notices and wonders that you can cross off the list right away. Things like “I wonder whether we will get any gummy worms?” can be addressed right away to show students that we are indeed listening to their noticing and wondering and that we value student voice.

After we have heard students and demonstrated that we value their voice, we can land on the first question we’ll challenge them with:

How many gummy worms are in the jar?

Follow up that question with:

How might we convince someone that the quantity you come up with is correct?

We can now ask students to make an estimate (not a guess) as we want them to be as strategic as they can possibly be. This will force them to use spatial reasoning alone to try and come up with an initial estimate and to share it with their neighbours by trying to articulate why they believe their prediction is reasonable.

Consider asking students to think about a number that would be “too low” and a number that would be “too high” before asking for their best estimate in order to help them come up with a more reasonable estimate.

Let them chat with their neighbours and challenge them to an estimation duel or a math fight.

Monitor student thinking by circulating around the room and listening to the mathematical discourse.

Encourage students to use precise mathematical language (including greater than, less than, more, less, half, rows…) and positional language (in front, behind, on top…) to articulate their defense.

If students’ estimates are unreasonable, encourage them to select a manipulative similar in size to the gummy worms (perhaps a relational rod) and ask them to lay out that number of items in front of them to consider whether that quantity seems reasonable.

After allowing students to share their estimates with neighbours and writing them down on the chalkboard/whiteboard/chart paper, let’s give them something to celebrate about with our first reveal:

Answer: 25 gummy worms.

Revisit the student answers. Ask students why their answers may or may not have been exact.

Celebrate the closest estimate in the way that you typically do in class. One such method might be doing a “1, 2, 3, CLAP!” for those who were closest.

Also make a special note to congratulate some of the students who weren’t so close and ensure that they know that we are building our estimation skills through this process.

Since we’ve already taken some time to set the context for this problem and student curiosity is already sparked, we have them in a perfect spot to help push their thinking further and fuel sense making.

Now that the context is already set, we’re good to start pushing the thinking and it is likely that any additional noticing or wondering will not be necessary at this point in the lesson.

Show them the following video where all of the gummy worms are placed back into the jar and then some are removed.

The question we’ll try to figure out is:

How many gummy worms are left in the jar?

Keep in mind, you can modify what question(s) you ask depending on what mathematical thinking you are looking to elicit. For example, you could also ask:

How many gummy worms were taken from the jar?

Having students estimate is always fun, but it is probably not necessary to have them estimate and share out at this stage like we did in the previous portion of the task. However, proceed or pivot as you see fit here.

In this task, students will have an opportunity to reason through a subtraction scenario. This particular problem is an example of the “removal” subtraction structure, often referred to as “take away”. This task will allow students to apply a variety of strategies and models, while developing a deeper understanding of big ideas, including the following;

• Part-whole relations: Relationships between addition & subtraction.
• One-to-one correspondence.
• One structure of subtraction is “removal”.

Login/Join to access the entire Teacher Guide, downloadable slide decks and printable handouts for this lesson and all problem based units.

Login/Join to access the entire Teacher Guide, downloadable slide decks and printable handouts for this lesson and all problem based units.

Login/Join to access the entire Teacher Guide, downloadable slide decks and printable handouts for this lesson and all problem based units.

Login/Join to access the entire Teacher Guide, downloadable slide decks and printable handouts for this lesson and all problem based units.

Login/Join to access the entire Teacher Guide, downloadable slide decks and printable handouts for this lesson and all problem based units.

After consolidating the learning by monitoring, selecting, and sequencing student work, have those students whose work will help expose different mathematical models. You can sequence in many ways, but a common method is from most accessible solution strategy to least accessible.

Then, share the second reveal video.

Answer: There are 17 gummy worms left in the jar

Revisit student answers and approaches.

Login/Join to access the entire Teacher Guide, downloadable slide decks and printable handouts for this lesson and all problem based units.