This Problem Set is a part of the Lesson 26, Unit 2, Grade 1. In this lesson, students begin understanding ten as a unit: "a ten". They rename their Rekenrek bracelet, the ten-frame, the fingers on two hands, and two 5-groups as 1 ten. They connect teen numbers to the unit form (for example, 1 ten and 1 one, 1 ten and 2 ones) and represent the numbers with Hide Zero cards.