Identify 10 more, 10 less, 1 more, and 1 less than a two-digit number.

In this lesson, students use Rekenrek bracelets, linking cubes, and drawings to find 10 more, 10 less, 1 more, and 1 less than a given number. Then they begin to explain the patterns that they see. For example, "I see that 10 less than 34 is just 1 less ten, so it must be 24." Students represent how the number changed using arrow notation.