Lesson objective: Students will be able to add a two-digit number with a multiple of ten by adding tens with tens and ones with ones.

Students bring prior knowledge of place value from 1.NBT.B.2. This prior knowledge is extended to adding two-digit numbers as students determine which combinations of numbers add up to a specific total. A conceptual challenge students may encounter is decomposing and composing numbers.

The concept is developed through work with cubes and written notation, which allows students to have access to both concrete and abstract representations of the concept.

This work helps students deepen their understanding of numbers because they will use the place of a digit to determine its value.

Students engage in Mathematical Practice 5: Use appropriate tools strategically as they choose their preferred representation in order to solve.

**Key vocabulary:**

- digit
- ones
- ones' place
- place value
- tens
- tens' place

**Special materials needed:**

- snap cubes (towers of 10 and loose cubes)