This Fluency Activity is a part of the Lesson 21, Unit 5, Grade K. Saying "bop" after each row of 10 provides a pause in counting, both reinforcing the start of a new row of ten and interrupting the count sequence, which helps students when they transition from counting all to count on in Grade 1. Sit in groups of 4. Put your Rekenreks together. Partner A moves the beads of the first row. Partner B moves the beads of the second row, etc.