Personal experience – How to prepare for a mental arithmetic test

How do you prepare for an upcoming mental arithmetic test? Everybody has their own approach, but I’ll share my personal story. Multiple trading firms start their interview rounds with a mental arithmetic test. Some tests are pretty well known, such as Optiver’s mental arithmetic test. They even bring their test to career days for you to try it out.

While you were reading that last sentence, were you stressed out because of the on-the-spot pressure thoughts? Or did you see think of this as a nice challenge? The mindset in this example is crucial for your preparations as well. Stop seeing this test as a test, it’s a challenge, it’s something fun. Mental arithmetics is definitely something you can train. People are not born as a human calculator, it’s all about exercising.

First of all: figure out what type of questions you’ll get. Does it contain decimals? How quick do you need to be on average? Does in contain fractions? These will give you an idea on how quick you should be during your exercises. For example, the Optiver math test contains 80 questions that need to be solved in 8 minutes. This is 1 question per 6 seconds. The biggest mistake you could make is to think: “Oh, so I can think 6 seconds about 1 question”. No, it doesn’t work like that. You’ll spend a second to read the question, a second to scan the multiple choice answers and a second to actually mark it with your pencil and shift your focus to the next question. This leaves you with a maximum of 3 seconds per question.

Now we know how quick we need to be, but how will we get there? You need to train two different aspects. The first and most obvious aspect is to be as quick and accurate as possible while exercising. The second aspect is about keep being consistent over the full 8 minutes. This has to do with both how long you can keep your concentration and how you deal with pressure.

Be as quick and accurate as possible

This sounds obvious, but it’s just step one out of three. Start with training on the easy mode on a two minutes duration. You should be able to dream entire multiplication schemes. For example, 7*8 may not cost you more than a second, you should “know” that it’s 56. You may start to “think” when you get the question 17*18. Some people go all the way with solving it at 10*18 + 7*10 + 7*8 = 306, but it’s even easier if you know when to take the shorter route: 20*17 – 2*17 = 306. Try to push yourself to two seconds per question on the easy level. Then you’re good for sure.


This is where you can start changing the settings and train on a longer duration. Train on 4 minutes, on 8 minutes. However, your average time per question should not decline. Use our tools to track your results, such that you can keep track of your progress. You can also exercise in a room where people are speaking loudly. This also helps to train your focus. Never forget: the circumstances during the real test can be sub-optimal for any reason.

Under pressure

This is where I became obsessive with my preparations. I remember when I was on a holiday with friends and we had a great night. The next morning: hangover. There is no better moment to train for your mental arithmetic test. These conditions, in which you don’t feel optimal, should still allow you to think fast and keep your pace with the exercises. Sit in a cafe where it’s loud and start exercising. Sit at the kitchen table while everyone is hanging out and start exercising. Sit in the train and start exercising. These sub-optimal environments will help you to survive during the real test, when things go slightly different. Did it really needed to be this though? Yes, I was a little ill during my test, and I aced it.