Final answer:
Newcomers like Cinna are assigned to District 12 because it is the poorest district and has a reputation for rebellion against the Capitol in 'The Hunger Games'.
Step-by-step explanation:
Newcomers like Cinna are assigned to District 12 in 'The Hunger Games' because District 12 is the poorest district in Panem, the dystopian society depicted in the book. District 12 is primarily known for its coal mining industry and has a reputation for being rebellious against the Capitol. Assigning newcomers to District 12 can be seen as a way for the Capitol to maintain control over the district and suppress any potential uprising.