I'll be 73 next month and was curious to see if I were more apt to use fluid or crystallized intelligence now. I looked at the example given at the Wikipedia link and solved it. Unfortunately, my solution was a third method, which simply tested two guesses for one legged show wearing men, which both gave the same answer, which immediately made me realize that any even number of shod one legged men would always give the same result, and also that this was an example of a particular type of math problem that tries to obfuscate the obvious.
I *think* that's more fluid, though it may be crystallized as I've always been in the habit of testing my solutions with multiple inputs and have seen that type of obfuscation in many puzzles and tests.
I think I'll have to look at real-world problem solving to get a feel for where my remaining intelligence is heading. My impression is that it is declining, sadly.