Lesson 13 of 1455
Chain-of-Thought: Make the AI Show Its Work
Telling the AI to 'think step by step' before answering dramatically improves its accuracy on reasoning problems. Here's why and when.
Builders · Prompting · ~14 min read
The four magic words
Adding 'think step by step' or 'let's work through this carefully' to a prompt can flip an AI from wrong to right on math, logic, and planning problems. Researchers call this technique chain-of-thought, or CoT.
With and without CoT
CoT turns a guess into a verifiable chain.
WITHOUT CoT: Q: A shirt costs $20 and is 25% off. Then you use a $5 coupon on the discounted price. What do you pay? A: $10. <-- often wrong WITH CoT: Q: A shirt costs $20 and is 25% off. Then you use a $5 coupon on the discounted price. What do you pay? Think step by step. A: - Original price: $20. - 25% of $20 is $5. - Discounted price: $20 - $5 = $15. - Apply $5 coupon: $15 - $5 = $10. Final answer: $10. <-- shows reasoning, more reliably correctHere the final number is the same, but with CoT you can check each step. If a step is wrong, you see it. Without CoT, the AI could give you '$15' and you wouldn't know why.
Phrasings that trigger CoT
- 'Think step by step.'
- 'Let's reason through this carefully.'
- 'Before giving your final answer, write out your reasoning.'
- 'Work it out one piece at a time.'
- 'Show your thinking as a numbered list, then give the answer.'
When to use CoT
Compare the options
| Use CoT | Skip CoT |
|---|---|
| Multi-step math. | Quick factual lookup. |
| Logic puzzles. | Creative writing. |
| Planning and scheduling. | Short answers or summaries. |
| Comparing options. | Simple translations. |
| Anywhere getting it wrong would matter. | Anywhere speed matters more than accuracy. |
Structured CoT — you can verify each step.
You are a careful tutor. A student asks: "I have 3 tests coming up. Math is worth 20%, Science is worth 35%, and History is worth 45% of my grade. If I scored 92, 78, and 85 respectively, what's my final grade?" Before you give a final number: 1. Write out what each score contributes. 2. Show the math. 3. Only then give the total. Format: **Step 1:** **Step 2:** **Step 3:** **Final grade:**Key terms in this lesson
End-of-lesson quiz
Check what stuck
8 questions · Score saves to your progress.
Lesson help
Questions are best handled with a grown-up here.
For this age range, Tendril keeps freeform AI chat paused until parent/guardian consent and child-safe moderation are fully verified. Use the quiz, notes, and related lessons below, or ask a parent, guardian, teacher, or librarian to work through the question with you.
Progress saved locally in this browser. Sign in to sync across devices.
Related lessons
Keep going
Builders · 40 min
Chain-of-Thought for Builders: Make AI Show Its Reasoning
Force AI to explain its reasoning out loud, and you'll catch its mistakes faster.
Builders · 26 min
Few-Shot Prompting: Teach by Example
Instead of describing what you want, show the AI two or three examples. Few-shot prompting is often the fastest way to get consistent output.
Builders · 25 min
System Prompts vs User Prompts
Every AI conversation has two layers: a system prompt that sets the rules, and user prompts you type. Understanding the difference is the gateway to building AI-powered tools.