Module 3 · Files, tools and your own data Lesson 9 of 15
Visible reasoning — and the open weights behind it — DeepSeek's own feature
Two things together. The reasoning is on screen, so you can check the step where an answer went wrong instead of guessing; and the core weights are published, so the same model can run on your own machine or your own server.
The concept
Because the working is where the learning is. A bare answer tells you what to write; the working tells you how to think, and it makes a wrong answer diagnosable rather than mysterious. That is worth more for an exam or an interview than a marginally better final line.
Turn reasoning on for anything with steps, and off for everything else. Read the working from the end backwards, hunting for the first step you disagree with. Correct that step in a follow-up and let it redo only from there.
Here is the shape of it, in the form you will actually use:
Reasoning: ON
A shop sells two products. Product A sells for 249 rupees and makes a 24% profit.
Product B sells for 399 rupees and makes a 12% profit. A customer buys 3 of A and
2 of B.
What is the total profit in rupees?
Show every step. State any assumption you make. Put the final answer on its own
line prefixed with ANSWER. If a step has two possible readings, solve both and
say which is more likely and why.Common mistakes
The mistake is using reasoning mode for everything. It costs time and tokens for no benefit on the other eighty per cent of your requests.
Worked example
A statistics question comes back with six numbered steps, one of which is the wrong distribution. You correct that step, not the question, and the second answer is right.
Your practice task
Take one past exam question you got wrong, run it with reasoning on, and find the exact step where your method and the model's differ. That difference is your gap.
Do this before moving on. Reading a solution teaches the shape of it; typing it teaches you.
Key takeaway
Because the working is where the learning is.
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