Call two students to the front of the room and ask the class how many noses they see. Ask for a volunteer to write the number sentence that shows that on the board. [1 + 1 = 2.] Now ask the class how many eyes they see, and call for a
volunteer to write that number sentence [2 + 2 = 4] on the board directly under the previous equation. Now, have each of the two students in the front of the room hold up three fingers, then have a volunteer record the relevant number sentence [3 + 3 = 6]. Then ask both students to hold up four fingers, then five fingers, and then six fingers. Call on a volunteer to write each number sentence on the board.
Ask the class what these kinds of facts are called. [Doubles.] Then point to the calendar and ask how many days are in two weeks, then add the doubles fact 7 + 7 = 14 to the list on the board. Next, call on eight students to wave their arms and ask someone else in the class to tell how many hands the class can see. Record 8 + 8 = 16 on the board. Finally, put 9 + 9 = on the board and ask the students what the answer will be [18]. Then, repeat with 10 + 10 =. Ask the students to look at the sums to see whether they notice a pattern. [Possible answers are that all the sums are even or that the sums increase by 2.]
Next to 2 +2 = 4, write 2 + 3 =, and ask the students what the answer will be [5]. Call on volunteers to explain how they know. Repeat with other doubles-plus-one facts up to 9 + 10 =. Encourage the students to say both the doubles and doubles-plus-one facts aloud.
Now assign the students to groups of four students each, and give each group two number cubes and a copy of the Tossing Sums activity sheet. Tell them to take turns rolling the number cubes and making an X in the column that shows which sum they rolled, beginning at the bottom of the sheet. As they play, you may wish to move around the room, noticing which students can name the sum immediately, which students count on their fingers, and which students need to use counters or other external aids, such as manipulatives.
After the students have played for several minutes, call the students together and ask them what sums came up most often. Then have them identify the sums that can be obtained only by getting doubles [2 and 12]. Now, assign each group one of the other even sums (4, 6, 8, or 10) and have them list all the ways they could get that sum. Then, ask them to circle the double. Encourage them to share their work with the class. Repeat with odd sums, having them circle doubles-plus-one sums.
Next, ask them to return to their seats and take out their personal addition charts. Ask them to add to their charts any facts that they now know from memory. Then have pairs of students exchange charts and ask each other the facts that are marked on the chart. If a student misses a fact, ask the partner to make a small dot or check mark by the fact to indicate that he or she needs to practice it further.
As a record of this lesson, have the students write two addition facts that they have recently learned and two facts that they wish to learn next.
