Lesson objective: Add and subtract numbers written in scientific notation using properties of operations.

This lesson helps to build fluency with adding and subtracting numbers written in scientific notation. A number line is used here because it highlights the relative size of really big numbers. This work develops students' understanding that because scientific notation is an equivalent form of numbers, we can perform operations with numbers written in this form using the properties of operations.

Students engage in Mathematical Practice 2 (reason abstractly and quantitatively) as they use what they know about properties with rational numbers and figure out how they can work for numbers written in scientific notation.

**Key vocabulary:**

- base
- distributive property
- exponent
- factor
- power of ten
- product
- scientific notation