Lesson objective: Students will be able to apply what they know about missing addend problems and composing a new ten to solve for missing numbers.

This lesson provides an opportunity for students to apply their knowledge and understanding of composing a new ten to a mathematical situation. Students are asked to find out how many rocks each student in the rock club collected on their nature walk.

Key Concept students will use:

- When adding two-digit numbers, we can compose a new ten from ones.

Skills students will use:

- Composing ten (Grade K, Unit 12)
- Using objects and drawings to represent and solve situational problems (add to, take from, put together, take apart, and comparing with unknowns in all positions) involving addition and subtraction. (Grade 1, Unit 9)
- Counting on or make ten to add and subtract (Grade 1, Unit 1)

Students engage in Mathematical Practice 5: Making Sense of Problems and Persevere in Solving Them as they apply knowledge about missing addends in a new context. Students will need to demonstrate perseverence as they understand that there is a piece of information missing and that there are various strategies that can be used to find that information.

**Key vocabulary: **

- one
- part
- ten
- whole

**Special materials needed:**

- cubes
- ten frames