Parrish (2010) describes number talks as classroom conversations around purposefully crafted computation problems that are solved mentally. The problems in a number talk are designed to elicit specific strategies that focus on number relation- ships and number theory. Students are given problems in either a whole- or small-group setting and are expected to mentally solve them accurately, efficiently, and flexibly. By sharing and defending their solutions and strategies, students have the opportunity to collectively reason about numbers while building connections to key conceptual ideas in mathematics. A typical classroom number talk can be conducted in five to fifteen minutes. (Parrish 2010, xviii)
Parrish, Sherry. 2010. Number Talks: Helping Children Build Mental Math and Computation Strategies—Grades K-5. Sausalito, CA: Math Solutions.