Many developers who don't come from a CS or Math background will run from such questions for the following reasons: 1) They've never solved problems like this

Many developers who don't come from a CS or Math background will run from such questions for the following reasons: 1) They've never solved problems like this with code before. 2) They fail to grasp how such problem solving skills can judge their "real world" experience. 3) Someone across the street/city/village will pay them more than you are paying and have more softball interview questions because they are more desperate to bring in any programming talent they can find. While reasons 1 and 2 are good reasons to pass on candidates, reason 3 is unfortunately a bigger challenge to solve. It may be unpopular to say this, but I would take a hard look at the problems you need your developers to solve and come up with a more real world scenario to use for interviews and see if you get better results.