Question preview
All-black? is a cooked quant interview question on puzzles.
Join to unlock this question, detailed solutions, and our complete library of quant finance interview prep.
This is a straightforward combinatorics problem that appears in quant interviews as a warm-up to check basic comfort with counting and the binomial coefficient. It requires you to set up the problem cleanly, identify the relevant cases, and avoid double-counting.
The core skill being tested is whether you can translate a natural-language constraint ("either all red or all black") into mathematical cases, then apply the combination formula correctly to each case before aggregating the results. Interviewers use questions like this to see if you think systematically about what "unordered" means and how to handle mutually exclusive outcomes.