Optiver Derivative Trader interview questions

Applied online, and a few weeks later received an invite to take the mental math assessment. I thought it was very easy, and finished all 80 questions with about 30 seconds to spare (I'm sure I missed a few though). I passed the assessment and then set up a behavioral phone screen with HR. While we were scheduling, I had an exploding deadline and asked Optiver if we could speed up the process. They said they could move the process faster and have an answer within a week. The behavioral phone screen was routine, and I was told I was moving on. Normally there are two more technical phone screens, but since I was expediting the process, I had both at the same time. I thought the technical phone screens were fair, though I completely botched an easy probability problem. Unlike the other interviews I have done (and I interviewed at three other places), the person on the other end did not help me during the mistake or even point out that I was making one. (Later, I solved the problem and it was quite easy). He also emphasized me estimating answers, so turning fractions such as .59/.73 into decimals without a calculator. We then moved to an "estimation" problem, where he asked me to compute the volume of salt in the Atlantic Ocean. I think my thought process was reasonable and efficient, although I could have been horrendously off, who knows. Then we moved to quick estimation problems, where he valued speed over accuracy and wanted me to give answers in hundredths of a percent (so an answer of two would come out to 20,000). I estimated very quickly, definitely wrong on some of them. For example, give 100 divided by 370000 in ten-thousandths. I received an email the next day saying I was not moving forward. I was a little surprised, because that same day I receive a full time offer at Jane Street (which is considered to be much harder to get), but I was unconcerned because Jane Street was my number one choice anyway.

The process was extremely quantitative, and quite rigorous. It consists of 80 math questios (mostly mental math) that you have 8 minutes to do, and if you don't hit a certain level then you are out. The next series of interiews is in Chicago, where there is an entire day of mental math and interviews.