Final answer:
The Louisiana Purchase indeed doubled the size of the United States, making the statement true.
Step-by-step explanation:
The statement in exercise 11.1.5 that the Louisiana Purchase doubled the territory of the United States is true. The 1803 purchase from France nearly doubled the size of the United States at the time, adding approximately 828,000 square miles of land west of the Mississippi River, including the entire area of what is now Louisiana and extending northward to the Canadian border and westward to the Rocky Mountains.