This Problem Set is a part of the Lesson 15, Unit 5, Grade K. In this lesson, students work to know number names and the count sequence. They count up and down by tens to 100 both the regular way (10, 20, 30) and the Say Ten way (ten, 2 tens, 3 tens). Use of a 100-bead Rekenrek by the teacher, and 10 small 10-frames for students support this work.