Final answer:
The maximum length of the rolled-up poster that can be mailed in the given box is 20 inches. This calculation is straightforward as it is determined by the longest dimension of the box.
Step-by-step explanation:
To determine the maximum length of the rolled-up poster that Chris can mail within a box measuring 20 inches by 8 inches by 4 inches, we need to find the longest dimension of the box. As the dimensions are 20, 8, and 4 inches, the longest side is 20 inches. Therefore, the maximum length of the rolled-up poster that can fit into the box is 20 inches long.
However, let's address the information provided in Figure 3.1.4.1 for the situation where Jesse is tasked with sending a package. Jesse should use the most convenient metric unit of mass to weigh the package, such as kilograms or grams, depending on the total weight of the 10 books and documents.