Teacher copy: This page may include teaching prompts or answer keys. Answer keys in this public library can be viewed by anyone. Give learners a clean prompt, use checks as formative evidence, and change a case locally when prior access matters.
35 = 3 + 7 + 12 + 8 + 5. Goal: rebuild Source B and verify both margins.
0–3: Name pattern family and border status as categorical variables; paper tiles, not people, are the unit.
3–10: Model Hatch row 14+4=18, pass column 14+9+2=25, and grand total 25+23=48.
10–22: Learners reconstruct the blank register, checking 18+18+12=48 and 4+9+10=23. Label Solid as a known category, not a missing observation.
22–30:Routes: counters in a tactile matrix; large-print table with margins; verbal/digital table and two-direction arithmetic. A partner chooses one cell and requests the source line.
30–35: Exit: “How many all paper tiles passed?” Key: 25 of 48. Move: if 23/36 is called all, circle the 12 Solid records in B.
Alternate domain: Fictional book-cover draft motifs and crop status. Optional/home: make a safe two-by-two table of invented paper tiles.