standard_description: Prove theorems about triangles. Theorems include: measures of interior angles of a triangle sum to 180°; base angles of isosceles triangles are congruent; the segment joining midpoints of two sides of a triangle is parallel to the third side and half the length; the medians of a triangle meet at a point.
problem_activity: Narrative
The purpose of this activity is for students to play Stage 4 in the Shake and Spill center, which was introduced in an earlier unit. This activity supports students in finding the missing part of an equation in a later activity.
Students use 3, 4, or 5 counters. They see some of the counters and determine how many more counters are under the cup. Students write an expression to represent each composition and decomposition.
Representation: Access for Perception.
Synthesis: Use a cup and two-color counters to demonstrate that there is 1 yellow counter hiding under the cup.
Supports accessibility for: Conceptual Processing, Visual-Spatial Processing
Required Materials
Materials to Gather
Cups
Two-color counters
Materials to Copy
Shake and Spill Stage 4 Recording Sheet Kindergarten
Launch
Groups of 2
Give each group of students a cup, 5 two-color counters, and two recording sheets.
“We are going to play Shake and Spill, Cover.”
If needed, review and demonstrate the steps of the center.
“Take turns with your partner spilling and covering the yellow counters. On each turn you can decide to use 3, 4, or 5 counters. Make sure you and your partner agree on how many total counters you are using before you shake, spill, cover, and record.”
Activity
8 minutes: partner work time
Student Facing
Put 3, 4, or 5 counters in the cup.
Shake and spill the counters.
Hide some of the counters under the cup.
Figure out how many of the counters are hidden.
Write an expression.
Student Response
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Activity Synthesis
Display the number 3 and the expression
\(2 + \underline{\hspace{1 cm}}\)
.
“Han and Mai spilled 3 counters and hid the yellow ones. This is what they wrote on the recording sheet. What is missing from the expression? How do you know?” (1 is missing. 2 and 1 are the parts that go together to make 3. If they can see 2 red counters, 1 yellow counter is hiding under the cup.)


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