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Compare cereal sizes by unit price with your store discount
Practice: Giving the right context. About 5 minutes.
About this exercise
You're deciding which cereal box to stock up on. Your loyalty card takes 10% off the store brand at checkout (the shelf tag doesn't show it). Write exactly 3 numbered lines, each showing price ÷ ounces = cents per ounce (apply the discount first where it counts), then one unnumbered last line: Buy: [option]. Plain text, under 60 words.
Common mistakes when you ask AI for this
- Not mentioning the card. The AI uses shelf prices, so the warehouse pack wins. Try: Add: "My card takes 10% off the store brand."
- Not asking to see the work. Unit prices are easy to fumble without the division shown. Try: Add a line to copy: "1. Name brand: $4.68 ÷ 18 = 26¢/oz"
- Getting a shopping guide. The AI adds tips about bulk buying and taste tests. Try: Add: "Then one line: Buy: [option]. Nothing else."
- Trusting the AI to count words. AI is bad at counting. Ask for a total word limit and it often lands over it. Try: Cap each line: "each line under 14 words."
- Forgetting where it goes. AI loves markdown tables and bold, which show up as clutter in a shopping list app. Try: Add: "Plain text, no bold, headings or tables."
What a strong prompt includes
- Mentions the discount
- Asks for unit price
- Asks to show the math
- Sets a word limit
- Asks for plain text
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