I've used a very similar method for myself in hiring remote workers, although my ratios are more extreme. In some cases we tested over 200 people and selected

I've used a very similar method for myself in hiring remote workers, although my ratios are more extreme. In some cases we tested over 200 people and selected one person for the job. Have not used math questions at this stage as it seems a bit too obtuse and not to-the-point. Better to ask an actual coding question if you are hiring a coder. However I have had success in hiring people that have been involved in maths olympiads or also in coding competitions.