This Instructional Activity is a part of the Lesson 11, Unit 7, Grade 8. This task is analogous to a previous activity with positive exponents. The number line strongly encourages students to think about how to change expressions so they all take the form b × 10^k, where b is between 1 and 10, as in the case of scientific notation. The number line also is a useful representation to show that, for example, 29 × 10^(-7) is about half as much as 6 × 10^(-6). The last two questions take such a comparison a step further, asking students to estimate relative sizes using numbers expressed with powers of 10.