Sometimes mathematicians are also useful in the industry because if the way learned to reason and solve problems. Math studies require the ability to focus on one problem and find the most efficient solution for this, it requires rational thinking (als logic is also a great part of mathematics) and mathematicians are used to not being able to solve a problem on first sight but to think and riddle about it to get it done. These qualities are useful in a lot of fields, e.g. I know a lot of Managers and Consultants who a mathematicians but obviously mainly use their soft skills instead of the math part they have learned.
Latest Answers