Landmark numbers are familiar landing places that make solving math problems easier, such as multiples of tens or hundreds. Familiarity with these numbers is vital to understanding numbers and their relationships with one another.
Students who learn about taking apart and putting together 10, 100 and 1000 and their factors gain knowledge that allows them to come up with their own logical problem-solving strategies. They are also better equipped to develop accurate estimation strategies. For example, when asked to multiply 25 by 17, a student familiar with landmark numbers may use the knowledge that there are four 25s in 100 to solve the problem mentally.