This Problem Set is a part of the Lesson 5, Unit 4, Grade 1. 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."