In the English language, the preposition to use before numbers largely depends on the context. Generally, "of" is used when referring to a part or a percentage, while "in" is used when indicating a quantity within a larger set. For instance, "50% of the population" and "50 in 100" are correct usages. This distinction is crucial for clarity and correctness in written and spoken English.

The use of prepositions before numbers is governed by grammatical rules and conventions. According to the American Heritage Dictionary, "of" is used to express a part-to-whole relationship, such as "one-third of the class" or "20% of the total." This preposition signifies a proportion or a fraction within a larger whole. On the other hand, "in" is used to denote a quantity within a specific set or collection, as in "three in ten" or "seven in a group of eight.

Data from the Modern Language Association (MLA) and the Associated Press (AP) style guides support these conventions. The MLA Handbook states that "of" is used when expressing a part of a whole, while the AP Stylebook emphasizes the use of "in" when referring to a quantity within a set. These guidelines are widely followed in academic and professional writing in the United States.

For example, in a statistical report, one might say, "The survey indicates that 30% of respondents prefer option A," using "of" to express the proportion of respondents. Conversely, when discussing a specific number within a set, such as "There are 30 in the sample," the preposition "in" is appropriate.

Understanding the correct preposition to use before numbers is essential for effective communication in English. Misusing prepositions can lead to confusion or misunderstandings, especially in contexts where precision is crucial, such as scientific research, business reports, or legal documents. Therefore, adhering to the established grammatical rules and style guides is vital for clear and accurate expression.