This Problem Set is a part of the Lesson 4, Unit 6, Grade 1. In this lesson, students recognize that numbers such as 67 can be interpreted as 6 tens 7 ones and that the units can be combined to find the total: 60 + 7 = 67. This work of decomposing and composing 67 into its tens and ones supports the work students do in upcoming lessons, as they decompose two-digit numbers before adding to another two-digit number.