Goal: find a forward increase and return decrease without assuming equal percentages. 25 = 2 + 5 + 6 + 7 + 5.
- 0–2: Read Card L's two invented list versions: $125 then $137.50. This is not observed inflation.
- 2–7: Model increase
$12.50;12.50÷125=0.10=10%. Put original $125 under the fraction. - 7–13: Return direction uses
$12.50÷137.50≈9.09%decrease. Learners show why a 10% decrease from $137.50 would not land exactly on $125. - 13–20: Routes: place same $12.50 difference against two differently sized base strips on the change ladder; annotate two fraction boxes; calculate and explain both directions orally/typed. Every route identifies the new start and the invented-data boundary.
- 20–25: Exit “Same dollar change: same percentage?” Key: no, because the starting bases differ. Move: underline “from” in each sentence before choosing a denominator.
Alternative domains: fictional festival supply list or book-cover estimate. Optional/home: invent a $50→$60 change and reverse it; no actual inflation claim. Two optional swaps.