Lesson objective: Understand that ten ones are equal to one group of ten, and we can unitize objects in order to count groups more easily.
Students bring prior knowledge of ten ones from K.NBT.A.1: Compose and decompose numbers from 11 to 19 into ten ones and some further ones. This prior knowledge is extended to grouping 10 ones into a group of 10. A conceptual challenge students may encounter is accepting that 10 ones, or items, can be represented as one unit of ten, and then counted as one group.
This lesson emphasizes the concept that a bundle of ten ones is called "a ten." This is called unitizing and is foundational to students' ability to count groups as though they were individual objects. In this unit, students begin to make a shift in their understanding of counting and our place value system. Now students may count "10, 20, 30," saying only 3 numbers but having counted 30 objects. This shift in thinking requires time and rich experiences with concrete manipulatives to develop. Experiences with concrete manipulatives will help to build students in their understanding of number conservation. For this reason, it is important to provide ample time with cubes and other counters on ten frames, rather than using pre-grouped tools like base ten blocks or bean sticks.
Like in Lesson 1 of this unit, the concept of making a ten is developed through work with counters, representations, and ten frames. This work helps students deepen their understanding of equivalence as they notice that 10 ones are equal to one group of ten, or one ten. Students will continue this work throughout the year as they develop addition and subtraction strategies, compare numbers, and count by tens.
Students engage in Mathematical Practice 7 (Look for and make use of structure), as they repeatedly make bundles of ten using objects and by drawing in ten frames. Students are asked to verbalize the concept that ten ones makes one ten. Visualization of one unit of ten is developed as they see, and work with, various representations in the forms of a box of cupcakes, a ten frame, and other "grouped" objects.
Key vocabulary:
- bundle
- group
- single
- ten/ "a ten"
- ten frame
Special materials needed:
- cubes or counters
- ten frames (See Additional Materials)
About mini lessons:
- Mini lessons are short lessons, often focused on a key strategy, that are intended to complement instruction for certain key concepts.
- Mini lessons are designed to take between 15 and 20 minutes and can be used flexibly. While mini lessons are suggested in the sequence of a unit, they can be used at the teacher's discretion depending on the needs that arise from students.
- For example, teachers might use a mini lesson immediately after a conceptual lesson to solidify understanding of a new idea or to give students a new way to think about the concept. Teachers might also use a mini lesson as part of a number-talk or warm-up routine prior to beginning the day's instruction. In other classrooms, teachers may decide to use the mini lesson for certain small groups while other students engage in practice or center work.