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Compare two used cars by three-year cost

  • For Freelancers and creators
  • You practice Showing an example of what you want
  • Time about 5 minutes

About this exercise

You're choosing between two used cars and want the full cost over 3 years, not just the price. For each car, add price (including any fees in the fine print), insurance for 36 months and fuel for 36,000 miles at $3.50 a gallon. Get exactly 3 numbered lines in plain text, under 100 words: one per car with the math shown, then which is cheaper over 3 years and by how much. Write a prompt that gets you exactly that.

Common mistakes when you ask AI for this

  • Missing the fine print. The AI uses Car B's $12,500 headline price and skips the $900 fee at the bottom. Try: Add: "Include Car B's $900 dealer fee from the fine print."
  • Comparing only sticker prices. The AI compares prices and mentions mpg in passing, but never adds three years of gas and insurance. Try: Say: "For each car: price + insurance x 36 + (36,000 miles / mpg) x $3.50."
  • No math shown. The AI gives totals you can't check. Try: Show it: "1. Car A: $14,000 + $110 x 36 = $3,960 + fuel $4,200 = $22,160".
  • Getting a buying guide. The AI adds resale value, features and inspection tips, echoing your uncle. Try: Add: "Line 3 only says which is cheaper and by how much. No advice."
  • Trusting the AI to count words. AI is bad at counting. Ask for "under 100 words" and it often lands well over. Try: Cap each part: "each line under 30 words."

What a strong prompt includes

  • Includes the dealer fee
  • Counts all three costs
  • Shows the math
  • Sets the number of lines
  • Sets a word limit

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