In previous lessons, students practiced adding and subtracting within 10. In this lesson, students use the methods that make the most sense to them to add and subtract within 20. The lesson activities encourage students to use methods such as using known facts, making 10 to add, decomposing a number to lead to a 10 to subtract, and using the relationship between addition and subtraction. This lesson helps students practice adding and subtracting with 20 and apply their fluency within 10 in preparation for their work with addition and subtraction in grade 2.
If students need additional support with the concepts in this lesson, refer back to Unit 3, Sections C and D in the curriculum materials.
Activity 1: Muchas formas de sumar y de restar
- Add and subtract within 20.
- Sumemos y restemos hasta 20.