What’s inside:

• Part 1 · Set Your Smoothie Price — a live y = kx graph with a price slider; the table, equation, and gold unit-rate point (1, k) all update together. The $3 delivery fee toggle turns the line gold, lifts it off the origin, and the caption explains exactly why proportionality just broke.
• Part 2 · Proportional or Not? — random tables from three generators (true proportional, constant-difference trap, hidden-fee trap). Students commit before the reveal, then a gold y ÷ x ratio row appears in the table showing the evidence.
• Part 3 · Three Tycoon Machines — ⚖️ Unit Rate Machine accepts decimals, fractions (1/2), and mixed numbers (1 1/2), shows the “flip the fraction” reciprocal step, and gives both unit rates; 🧾 Checkout Machine walks discount → tax → tip, each on its correct base, with the “never mash percents together” warning; 🏦 Savings Machine does I = p·r·t with the percent-to-decimal step called out.
• Part 4 · Quiz — 10 questions spanning 7.RP.1 (complex unit rates), 7.RP.2 (tables, origin rule, k, y = kx, meaning of (1, r)), and 7.RP.3 (interest, discount+tax, percent change, increase-then-decrease). Four result tiers with tag-based routing back to the exact Part.

Misconception coverage summary: Questions 1 and 5 target division-direction errors — multiplying instead of dividing by a fraction, flipping x÷y for y÷x when finding rates and k — while Question 6’s distractors add the same reversal at the equation level (x = 4y, y = 4÷x). Questions 3, 4, and 6 target proportionality traps: constant difference mistaken for constant ratio, “any straight line is proportional,” and irrelevant features like steepness or direction, with Question 7 handling reversed coordinates and misreading (1, r) as a fee. Questions 2, 8, 9, and 10 target percent traps: forgetting to convert 5% to 0.05, mashing percents into one blob (25% − 8%), dividing percent change by the new value instead of the original, and believing +20% then −20% cancels out.