This math topic focuses on calculating the full or original value of a number based on a given percentage. Specifically, the problems involve determining what number a certain percentage (mostly in 10% increments, with examples involving 20% and 30%) represents. Each question presents a scenario such as "3 is 10% of a number" and requires finding the base from which the percentage is derived. This is an introductory level practice, primarily aimed at enhancing understanding of basic percentage calculations and their applications.