There are two main ways to structure a problem-solution essay. These are similar to the ways to structure cause and effect essays , namely using a block or a chain structure. For the block structure, all of the problems are listed first, and all of the solutions are listed afterwards. For the chain structure, each problem is followed immediately by the solution to that problem. Both types of structure have their merits. The former is generally clearer, especially for shorter essays, while the latter ensures that any solutions you present relate directly to the problems you have given.
 According to Paul Ratsmith, the tenuous, but nonetheless important, relationship between pumpkins and rats is little understood: "While I've always been fascinated by this natural kinship, the connection between pumpkins and rats has been the subject of few, if any, other studies" (2008).  Ratsmith has been studying this connection, something he coined "pumpkinology," since the early 1990s. He is most well-known for documenting the three years he spent living in the wild among the pumpkins and rats.  Though it is a topic of little recent interest, the relationship has been noted in several ancient texts and seems to have been well understood by the Romans. Critics of Ratsmith have cited poor science and questionable methodology when dismissing his results, going so far as to call pumpkinology "rubbish" (de Vil, 2009), "stupid" (Claw, 2010), and "quite possibly made up" (Igthorn, 2009).  Despite these criticisms, there does appear to be a strong correlation between pumpkin patches and rat populations, with Ratsmith documenting numerous pumpkin–rat colonies across North America, leading to the conclusion that pumpkins and rats are indeed "nature's best friends" (2008).