In this number talk, Mia Buljan engages her third grade learners with a one-digit by two-digit multiplication problem, 5x14. She comments that her students have shown that while some numbers are easier for them to decompose (for example, tens and fives), with other numbers it is more difficult for students to mentally identify “friendly” numbers to use to help solve the problem. She invites students to share the different solutions they found, and then defend their thinking.
In a debrief with coach and colleague Erika Isomura, Buljan notes that ambiguity of language can make this kind of mental math particularly challenging for learners: do they really understand the difference between three groups OF 36 and 36 composed of three groups?
Taught by: Mia Buljan, Glassbrook Elementary School, Hayward Unified School District, Hayward, California
- Operations & Algebraic Thinking