- Compose and decompose two-dimensional shapes, and show that the area of a shape remains constant regardless of how its parts are rearranged.
- Sort and identify two-dimensional shapes by comparing number of sides, side lengths, angles, and number of lines of symmetry.

- Read, represent, compose, and decompose whole numbers up to and including 200, using a variety of tools and strategies, and describe various ways they are used in everyday life.
- Estimate the number of objects in collections of up to 200 and verify their estimates by counting.

- This is a teacher led activity, which can be conducted with a whole class or small groups.
- Students must have previously been exposed to base ten materials, units and tens.

- Computer and projector
- Base Ten Block Challenge Slide Deck:
__Appendix A__ - Student response sheet, either:
- small whiteboard and dry erase marker (per student) or
- paper and pencil

- Base ten blocks (nine tens and nine units) for each student

In this quick image activity, students are presented with an image composed of base ten blocks. After viewing the image for five seconds, they are then invited to recreate the image from memory with their own base ten blocks. Then students calculate the sum of base ten materials used to create the image.

- To begin the lesson, review the base ten blocks and that a rod represents a ten, and a unit represents a one.
- Explain to the students that they will see an image composed of base ten blocks on the screen for five seconds.
- Present the first image (Figure 1) for five seconds and ask the students to recreate the image with their own set of base ten blocks from memory.
- Then ask the students to mentally calculate the sum, and write it on their individual whiteboards and hold their whiteboards for the teacher to see.
- When most of the students have held up their calculated sum, bring back the image on the screen, and ask the students to count with you to find the correct answer together. Begin with tens, pointing to each individual rod in the image, helping the students to count by 10s. Then continue to count with ones.
- Repeat with each item. Depending on the studentsâ€™ ability, you may choose to extend or shorten the display time of each item.

While the image is in full view of the students, you may ask all or some of the following questions:

- Was this image easy or difficult to remember and why?
- As we look at the image together now, what shapes do we see?
- Can you see any symmetries? Is there more than one line of symmetry?
- (For older students) Do you see any rotational symmetries?

- Ask students to create their own image to serve as a challenge to other students.
- Ask students to create their own image using their own base ten blocks.
- Photograph studentsâ€™ images to be used at a later time.

- Use the structure of this activity as a barrier game.
- Two children sit across from each other.
- One child creates an image with the base ten blocks.
- The child describes it to their partner and the partner tries to recreate the image based on the verbal instructions.

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