{"id":"study-cpi-inflation-rate-math","audience":"high-school","category":"explaining","technique":"examples","track":"study","title":"Calculate an inflation rate from CPI with the math shown","free":false,"task":"Your AP Macro problem asks for the inflation rate between two years. Get exactly 3 numbered lines: the formula with the corrected CPI values plugged in, the result as a percent, and one sentence on what it means for a $50 basket of groceries, plain text, under 75 words. Use the corrected 2024 CPI from Ms. Ito's post.","materialLabel":"The problem and teacher post (attached to your prompt automatically)","material":"AP MACRO - Ms. Ito - Unit 2: Inflation and CPI - Problem 6\n\nConsumer Price Index (CPI) for the town of Harlow:\n2023: 250\n2024: 270\n\nProblem 6: Calculate the inflation rate from 2023 to 2024.\n\nFormula: inflation rate = (CPI this year - CPI last year) / CPI last year x 100\n\n** Ms. Ito's post: \"Typo in Problem 6: the 2024 CPI is 260, not 270. Use 260.\" **\n\nMy confusion: I can plug in numbers, but I don't get what the percent means in real life.\n\nFrom class: \"If inflation is 4%, something that cost $100 last year costs about $104 now.\"\n\nNot this unit: real vs. nominal GDP (next week).\nProblem set due Friday.","rules":[{"type":"numberedItems","count":3},{"type":"maxWords","max":75},{"type":"plainText"}],"mistakes":[{"title":"Asking for an explanation","why":"The AI explains inflation in general and may skip your numbers.","fix":"Ask for the math: \"Plug the corrected CPI values into the formula.\"","checks":["r0"]},{"title":"Missing the correction","why":"The typo and the fix are both in your material.","fix":"Add: \"Use 260 for 2024, per Ms. Ito.\"","checks":["r0","r1"]},{"title":"Not saying how many lines","why":"The AI picks its own number, and it usually picks more lines than you need.","fix":"Be exact: \"Exactly 3 numbered lines.\"","checks":["numberedItems"]},{"title":"Skipping the meaning","why":"A percent alone doesn't answer what it means in real life.","fix":"Add: \"End with what it means for a $50 basket.\"","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 line: \"each under 20 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":"Asks to show the math","patterns":["show.{0,15}(math|work)","plug","260 ?- ?250"]},{"label":"Uses the correction","patterns":["260","correct","typo"]},{"label":"Says how many lines","patterns":["\\b(3|three)\\b.{0,25}line"]},{"label":"Asks what it means","patterns":["\\$50","real life","mean"]},{"label":"Sets a length limit","patterns":["\\d+\\s*words","word (limit|count)","under \\d+"]}],"hint":"Ask for the setup, the result and a real-life meaning on separate lines, using the corrected CPI value.","rubricLabels":["Line 1 shows the formula with the corrected numbers: (260 - 250) / 250 x 100","Line 2 gives the inflation rate as 4% (not 8%)","Line 3 explains in one sentence that a $50 basket would now cost about $52, with nothing about real vs. nominal GDP"]}