Lesson objective: Students will be able to add 10 to any 2-digit number without having to count on by ones.

Students bring prior knowledge of adding on to a number from K.CC.A.2. This prior knowledge is extended to adding on 10 more as students figure out how many beads would be on a necklace if 10 more were added on. A conceptual challenge students may encounter is that when adding on 10, the tens place changes and the ones place does not.

The concept is developed through work with cubes, which helps students see a model of adding on 10.

This work helps students deepen their understanding of operations because they will discover that when adding 10, the tens place changes while the ones place remains the same.

Students engage in Mathematical Practice 5: Use Appropriate Tools Strategicially as they use various strategies and representations in order to add 10 more.

**Key vocabulary:**

- add
- count on
- more
- ones place
- place value
- tens place

**Special materials needed:**

- cubes (towers of ten cubes and single cubes)