🕵️ Number Sleuths Case Files

The classroom becomes a detective agency. In teams, students open “case files” with 3–4 addition and subtraction problems within 20 and solve them using mental strategies (making ten, doubles, counting on). Students act out strategies with ten-frames, number lines on the floor, and counters. Introduce the Essential Question and explain that real library visitors and classmates will be our “users” whose strategies we need to understand before building puzzles for them.