Look for and make use of structure on the addition chart by looking for and coloring problems with the same total.

In this lesson, students continue exploring patterns among familiar facts on the addition chart. They examine patterns in expressions where the totals are the same. For example, given the sequence 5 + 5, 4 + 6, 3 + 7, 2 + 8, and 9 + 1, which forms a "staircase" on the addition chart, they notice that the total is 10 each time. Moreover, there are other staircases on the addition chart containing expressions that share the same total.