2nd Grade Crazy-Shaped Sandwiches- Halves Lesson #5
Common Core State Standard:
2.G.3. Partition circles and rectangles into two, three, or four equal shares, describe the shares using the words halves, thirds, half of, a third of, etc., and describe the whole as two halves, three thirds, four fourths. Recognize that equal shares of identical wholes need not have the same shape. / Common Core Math Practices
3. Construct viable arguments and critique the reasoning of others.
5. Use appropriate tools strategically
6. Attend to precision (in communication)
Materials:
  • Color tiles
  • 4x6 grid sheets- for students to color their half sandwich designs there are 2 versions.
  • (A) use with students who need to actually place tiles onto the grids and then color
  • (B) use with students who are able to look at their color tile arrangement and color the grid without needing to place tiles on the grids
  • Crazy-Shaped Sandwiches - Comparing Halves (1 sheet per partner group)
/ Vocabulary:
One-half,
half of,
equal share,
fair share
Lesson/ Workshop
Ask students to get 12 tiles of one color and 12 of another color. Ask them to use the tiles to make a “sandwich” that is half of one color and half of another.

Explain to students that halves need to be continuous.
If students split the halves apart, ask them to keep the sandwich all together.
Have students compare their sandwiches to others around them. Ask, “Are our sandwiches all the same?”
Next, ask students to record their sandwich design on grid paper provided. Challenge students to create as many different designs as possible following the guidelines above.
Once students have created several designs, ask them to cut out HALF of one of their sandwiches and bring it to the carpet. Seat students next to each other so that they have different-shaped halves.
Stop and watch the sharing video (it’s not in English, but you don’t have to know what they are saying to get the gist of the meaning).
After watching the video clip, ask:
  • What did you notice about the sandwiches they shared?
  • Did all of children get an equal share/half? How do you know? Etc.
  • At this point, revisit their generalization of “half”.
Tell partners to imagine that you are sitting at the table and you lift up your lid, you have your half and your partner has his/hers. Do you have the same amount? How do you know? How do they come together to make a sandwich?
Send partners to work on the Crazy-Shaped Sandwiches - Comparing Halves sheet.
Discussion
After partners have had time to explore bring them back together by having them discuss their strategies.
Here is a SMART Board file to help you display the images. The colored tiles on the right have been infinitely cloned.

  • How did you partition each sandwich?
  • How do you know that each region is one-half of the entire sandwich?

4x6 sandwich grids – version (A)


4x6 sandwich grids – version (B)

Crazy-Shaped Sandwiches- Comparing Halves

Partner Names:______

1. Go back to your desk and make your two halves with color tiles.

2. Are your halves equal? How do you know?

3. Do your halves make a whole sandwich? Use your paper halves to prove that your two halves make one sandwich. (You might need to cut and move squares). Glue your halves together in the space below.