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Split a loan payment into interest and principal and write the entry

  • For Small business owners
  • You practice Asking for a format you can use
  • Time about 5 minutes
  • Level Beginner

About this exercise

You're recording this month's loan payment. Write a prompt for plain text with lines starting "Interest:", "Principal:", "New balance:" and then three journal lines in the form "Dr 7100 Interest Expense 250.00". Interest is the balance times the annual rate divided by 12. Under 80 words. No bullets or numbering. Do not mention expensing the whole payment or any colleague's suggestion.

Common mistakes when you ask AI for this

  • Expensing the whole payment. The AI debits expense for $1,200. Try: Add: "Do not expense the whole payment."
  • Wrong interest. The AI uses the annual rate without dividing by 12, getting $3,000. Try: Say: "Interest = balance x annual rate / 12."
  • New balance error. The AI subtracts the full payment from the balance. Try: Add: "New balance = old balance minus principal."
  • Markdown extras. The AI adds bold labels, headings and a closing note. Try: Say: "Plain text, no bold. Output only the lines asked for."
  • Trusting the AI to count words. AI is bad at counting and runs past word limits. Try: Ask for fewer words than the real cap and keep each line short.

What a strong prompt includes

  • Names the first lines
  • Gives the interest formula
  • Gives the journal form
  • Bans expensing the payment
  • Caps length

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