Optiver Derivative Trader interview questions

Why trader? Why optiver?

We were 20 people in a class, an HR gave us a test with 80 questions in 8 minutes (6 second for each question, it is sooooo fast !!) . It is a multiple choices questionnaire, the question are easy mental calculus or easy equation, with some trick (for example you may find 1/3 for the answer but it won't be on the suggested choices you willl have instead 6/18) it seems easy but the time runs to fast. Each good answer worth +1, each false -1, each questions unanswered after the last one answered worth 0. You need to have a sore of 55-60 to pass. Actually just one of 20 succeded, he was invited to two other tests logic and brainteaser, with a little bit more time. Actually when the HR told 4 minutes remaining most of people haven't finished 20 questions of the 80.