{"id":"study-elasticity-campus-coffee-math","audience":"college","category":"explaining","technique":"grounding","track":"study","title":"Get price elasticity explained with the lecture's real numbers","free":false,"task":"Your Intro Micro professor used a campus coffee cart to show price elasticity, but the slide had a typo she fixed by email. Get an explanation in under 90 words, plain text, that shows the math with the corrected numbers (percent change in cups divided by percent change in price, simple percent method, not midpoint) and then says whether demand is elastic. End with one new practice problem with different numbers for you to try, without its answer.","materialLabel":"Lecture slide and professor's email (attached to your prompt automatically)","material":"ECON 1010 - Lecture 9 - Elasticity (Prof. Lindqvist)\n\nSLIDE 14: The Grind (campus coffee cart)\n- Raised a large coffee from $4 to $5\n- Cups sold per day fell from 400 to 340\n- Price elasticity of demand = % change in quantity / % change in price\n- We use simple percent change in this class: (new - old) / old. Ignore the sign.\n- Elastic: greater than 1 (buyers very responsive)\n- Inelastic: less than 1\n- Unit elastic: exactly 1\n\nMy note: we will NOT use the midpoint formula in this course, she said the textbook's version is \"overkill for us.\"\n\n---\nEMAIL from Prof. Lindqvist, Tues 8:14 PM\nSubject: Slide 14 typo\nHi all, slide 14 has a typo. Cups sold fell from 400 to 280, not 340. Please fix your notes before the problem set. - L\n\n---\nMy question: I keep getting confused about which percent goes on top. And is The Grind's demand elastic or not?\n\nGroup chat: Theo says coffee is \"always inelastic because people are addicted\" lol\nProblem set 4 due Friday 11:59 PM.","rules":[{"type":"maxWords","max":90},{"type":"plainText"}],"mistakes":[{"title":"Missing the professor's fix","why":"The typo and the correction are both in your material, and the AI may use the slide number.","fix":"Add: \"Use the corrected number from her email (280 cups).\"","checks":["r0"]},{"title":"Not asking to show the math","why":"The AI may give the verdict without the division, so you still don't know which percent goes on top.","fix":"Add: \"Show the math: % change in cups divided by % change in price, then the verdict.\"","checks":["r0","r1"]},{"title":"Reading instead of practicing","why":"An explanation feels clear until you try one yourself, and the AI won't give you one unless asked.","fix":"Add: \"End with one practice problem with new numbers, and don't solve it.\"","checks":["r2"]},{"title":"Trusting the AI to count words","why":"AI is bad at counting. Ask for a total and it often lands 20% over.","fix":"Cap each part: \"at most 4 short sentences, each under 18 words.\"","checks":["maxWords"]},{"title":"Forgetting where it will be read","why":"AI formats for a screen, with bold and headings that show up as stray symbols in your notes.","fix":"Say: \"Plain text, no bold, no headings.\"","checks":["plainText"]}],"promptHints":[{"label":"Uses the correction","patterns":["correct","email","280","typo"]},{"label":"Asks to show the math","patterns":["show.{0,15}(math|work|calculation)","divid","percent"]},{"label":"Asks for a practice problem","patterns":["practice","problem.{0,20}(try|me)","new numbers"]},{"label":"Sets a length limit","patterns":["\\d+\\s*words","word (limit|count)","under \\d+","sentences"]},{"label":"Asks for plain text","patterns":["plain","no bold","no markdown","no formatting","no headings"]}],"hint":"Your material has a typo and its correction. Tell the AI which numbers to use, to show the division before the verdict, and to leave you a problem to try yourself.","rubricLabels":["Uses the corrected numbers (400 to 280 cups, a 30% drop, not 340) and shows the math with quantity on top: 30% divided by 25% equals 1.2, using simple percent change, not the midpoint formula","Concludes that demand is elastic because 1.2 is greater than 1","Ends with one new practice problem using different numbers from The Grind's, and does not give that problem's answer or work it out"]}