The purpose of this activity is for students to recognize that even numbers can be represented as the sum of 2 equal addends. The activity is designed to elicit student curiosity about which types of decompositions are possible and which are not (with whole numbers). Students may notice many patterns in the ways even and odd numbers can be decomposed which will be useful in future lessons. However, the Synthesis should be focused on representing even numbers as sums of equal addends.

• “What did you notice about the possible ways the students could share their stickers?” (Kiran and Lin could share their stickers in the most ways. Noah could only share so that one friend had an even number of stickers and the other friend had an odd number of stickers.)
• Display:
• “How do these equations represent the student’s stickers?”
• “Which students have an even number of stickers? Use the equations to explain how you know.” (Kiran and Lin have an even number of stickers because the equations show you can split their stickers into 2 equal groups.)

The purpose of this activity is for students to represent even numbers as a sum of two equal addends. Students identify all whole numbers between 0 and 20 as even or odd and notice that all even numbers can be represented as a sum of two equal addends (whole numbers), while odd numbers cannot (MP8). Students may also use the sorting activity to understand and explain why 0 is an even number.

• “How did you decide whether this number is even or odd?”
• “How could you use counters or a drawing to show if this number is odd or even?”

• Display the completed table.
• “What do you notice about even and odd numbers?” (All the even numbers have the same addends. All the even numbers are “doubles.” The odd numbers have one addend that is 1 more than the other.)
• “Explain why even numbers can be decomposed into two equal addends.”