Second Grade - November 10th - 14th, 2008

Second graders are beginning to solve problems with bigger numbers. One problem we will look at this week is 12 + 24. Here are a few strategies we expect kids will discover as they solve this problem:

• Adding in Groups - Some students will start at 12 and count by ones 24 times. This method will work, but it becomes inefficient with large numbers. We would like to see kids who can start at 12 and add 10 at a time instead of 1 at a time. 12 + 24 can be thought of as 12 + 10 + 10 + 4.
• Breaking the Numbers Apart - Students may see that they can break the numbers 12 and 24 into (10 + 2) and (20 + 4). Since we just studied that order does matter when adding, we can rearrange our numbers to be (10 + 20) + (2 + 4). Now students are adding the tens together and the ones together. 10 + 20 = 30 and 2 + 4 = 6, so 30 + 6 = 36.