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PrepMint

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557 questions across 31 topics — each with a worked explanation. Start a timed set in ten seconds, get scored instantly, and see exactly where the marks went.

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Interview Prep

Interview preparation organised by skill domain rather than by job title, so what you revise maps to what you are actually assessed on.

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AI Tools & Coding Assistants

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Programming & CS

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Three question banks, one practice format.

  • Interview Prep

    Interview preparation organised by skill domain rather than by job title, so what you revise maps to what you are actually assessed on.

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    1
    subjects
    Topics
    1
    topics
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    40
    questions

557

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each with an explanation

31

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across 14 subjects

70

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Method, not motivation — how to actually work through a syllabus.

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  • How it works · 11 min read

    Why the model can't count the letters in a word

    Strawberry has two r's, your 100-word answer runs to 137, and the limerick does not rhyme. Those are not three mistakes. Text becomes tokens before the model sees it, and everything below the token — letters, characters, sounds — was discarded at the door.

  • How it works · 11 min read

    Why the agent stopped before it finished

    You asked for five things and got one, with a confident summary and no error. An agent loop ends when the model writes a message containing no tool call — a judgement nothing checks against your task. The five ways a run ends early, each fingerprint, and the phrasing that fixes it.

  • How it works · 11 min read

    Where you edit your prompt decides what it costs

    The session was fast for twenty turns, then you added one line to the top of a file and the next answer crawled. A prompt cache is keyed on an exact prefix, so cost and latency depend on where you changed something, not how much. The ordering rule that falls out of it.

Questions people ask

The short version: PrepMint is free, and you can start without an account.

Is PrepMint free?
Yes. Every test, every explanation and every topic page is free, with no trial and no paywall. Ads pay for it, which is why they are kept out of the test player entirely.
Do I need to sign up before I can practise?
No. Pick a topic and start — you will get your score and full explanations without ever seeing a login screen. An account only exists so that your history, streak and rank survive to the next visit, and you can create one afterwards without losing the attempt you just finished.
Can I see the answers before I submit?
No, and not by accident either: correct answers and explanations are never sent to your browser during an attempt. They load only after you submit, so practice measures what you actually know.
Are the questions written by AI?
They are AI-assisted and reviewed by a human editor before publication. Every question records how it was produced, and our editorial policy explains the process in full.
How is my score calculated?
One mark per correct answer, nothing deducted for a wrong one, and skipped questions score zero. Scoring happens on the server when you submit, and the timer is server-side too, so a slow connection or a refreshed tab cannot change the result.
What happens if I run out of time?
The attempt is submitted automatically with whatever you have answered, and the result page marks it as auto-submitted. Nothing is lost — answers are saved as you go, not at the end.

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