Interview practice

A practice mock interview for Oxbridge Maths and Computer Science

I’ve built an interview practice app on JZMaths for students preparing for Oxbridge Maths and Computer Science interviews.

You tackle an unfamiliar problem on a tablet whiteboard and think aloud as you work. The interviewer follows your working, listens, offers hints and asks you to explain your reasoning. Afterwards, you receive a written report and can explore the key ideas and full solution. I see this as the closest you can get to a real interview experience outside an actual mock interview.

I’ve prepared the questions, hints and interview structure; Claude AI runs the session within that framework. I may add more questions over the next few weeks.

It’s still early, and there are rough edges. But interviews are approaching, so I’d rather make it available now while it can help, and keep improving it along the way. Early feedback has been encouraging, and I’d welcome your honest thoughts if you try it. Every session gives you the opportunity to leave feedback, typed or handwritten, and I really appreciate it. My main goal is to make the app as useful as possible, and as more students use it, I’ll keep refining it based on their feedback.

For this interview season, I’m keeping prices low, mainly to cover my running costs. Each session currently costs me about $3 to $4 to run, including the API usage, so I can’t offer unrestricted free access.

Joe

What you practise

Thinking aloud. You speak as you work, as in a real interview: what you’re trying and why, and asking the interviewer when you’re stuck.
An unfamiliar problem. An open, interview-style problem rather than an exam question, worked on a whiteboard against the clock. Each problem is simply stated but needs deep thinking and reasoning to solve, and has extensions that challenge the strongest students further.
Taking hints. The interviewer nudges you when you’re stuck, steers you away from a dead end, or offers a new idea to see how you use it. Much of what interviewers look for is how well you pick a hint up and run with it, and this is hard to practise on your own. Hints are not meant to be immediately obvious to use! This is on purpose, and if you seem to be struggling, more specific help will be offered. So if a hint doesn’t seem straightforward, there’s a good reason for it — it probably means you’re doing well!
Explaining and justifying. Once you have an answer, you’re often asked why it works, and are expected to explain your reasoning carefully.

How a session works

Choose a question you haven’t taken. A few short cards explain the format, and the clock starts when you press Start.
Work on the problem for up to 45 minutes. The interviewer follows your board and what you say, and replies on screen. You can ask for a hint at any time, and the interviewer may offer one unprompted if you are struggling.
Your report is ready a minute or two after the end. It scores six areas that interviewers look at: insight, reasoning, fluency, persistence, learning from hints and, with your microphone on, communication.
Then carry on working if you like, and open the key ideas and the full solution.

Prices

Each credit is one session on one question. These prices are for this interview season.

Checking your account…

Good to know

Each question once. Each question can be taken once, so you can only buy as many credits as you have questions left. See the questions.
Pausing. You can pause a session and come back within a week; the clock stops while it is paused, and if the page closes or the connection drops, it pauses by itself.
Check your equipment first. You need a tablet with an active stylus pen, such as an Apple Pencil, in the Chrome app. A finger, or a plain rubber-tipped stylus, cannot write on the whiteboard. The app has been tested in Google Chrome, and other browsers may not work correctly. I’m sorry I haven’t yet had time to test other setups.
If the app fails. If a fault in the app prevents a usable session, email jzmaths@hotmail.com within 14 days and you’ll get a replacement credit, usually within 24 hours.
Changing your mind. Within 14 days of buying, you can have the credits you haven’t used refunded. Credits don’t expire.

Purchase terms

What you are buying. Interview credits for the JZMaths practice mock interview. One credit is one interview session of up to 45 minutes on one question of your choice. Each question can be taken once on an account, so you can only buy as many credits as you have questions left to take.
Price. £4 for one credit, or £18 for five credits (£3.60 a credit).
An early release. The practice interview is new and still being improved. The questions, the interviewer's hints and the reports may change as it develops.
Whose account. Credits are added to the JZMaths account that was signed in when the payment started. A parent, guardian or anyone else may pay; the credits still belong to that account. If you are under 18, please buy only with the permission of a parent or guardian.
What you need. A tablet with an active stylus (an Apple Pencil, or a stylus that works like one), in the Google Chrome app, with a steady internet connection, the microphone enabled on your tablet, and a quiet place to think aloud. A finger, or a plain rubber-tipped stylus, cannot write on the whiteboard. Please check your equipment before you buy: a session that cannot be used because the equipment does not meet these requirements is not a fault in the app.
How a session works. A session has 45 minutes of interview time and ends by itself when they are used. You can pause it and come back within 7 days: the clock stops while it is paused, and if the page closes or the connection drops, it pauses by itself. A session not resumed within 7 days ends, and its credit is used. Afterwards you receive a written report, and can carry on working and open the key ideas and the full solution.
If the app fails. If a fault in the app prevents a usable session (for example, the whiteboard does not accept writing from a suitable stylus, or the interviewer stops responding), email us within 14 days of the session and we will add a replacement credit to your account.
How long credits last. Credits do not expire. If we withdraw the practice interview, we will refund any credits you have paid for and not used.
Starting a session, and your right to cancel. An interview session is a service, provided when you start it. Before paying, you are asked to tick one box that agrees to these terms and the terms of use, asks for each session to be provided when you start it, including within your 14-day cancellation period, and acknowledges that you can't cancel a session for a refund once it has started. We record the wording you agreed to and when.
Cancellation and refunds. Your cancellation period runs until the end of the 14th day after the day of your purchase. To cancel within it, email jzmaths@hotmail.com with the email address associated with your JZMaths account. We will refund the credits from that purchase that you have not used, to the original payment method, within 14 days of receiving your notice. Any other request for a refund is reviewed individually. This does not affect your statutory rights.
If your purchase is refunded in full. The unused credits from it are removed. Sessions you have already taken, and their reports, are kept.
Personal use only. The questions, hints, key ideas and solutions are licensed to you personally for your own preparation, under section 4 of the terms of use. Please obviously do not share them.
Your information. What is recorded during a session, and who it is shared with, is set out in the privacy policy.

These terms apply alongside our terms of use (opens in a new tab). A copy is sent with your confirmation. Version 2026-11-interview-credits-v3.

Questions? Email jzmaths@hotmail.com