A collection of quant riddles with answers
There's a reference to the classic Heard on the Street book but you should also check out Zhou's green book, which consists a guide on cracking the type of interview questions Google used back in the mid 2000s/early 2010s (how many ping pong balls can fit in an airplane), with much more demanding problems though:    A Practical Guide To Quantitative Finance Interviews,  Xinfeng Zhou

https://www.amazon.com/Practical-Guide-Quantitative-Finance-...