I quickly came up with the incorrect answers for #1 and #2, but was able to realize that something was wrong with them and thought about it for a few more seconds and got the right answers.
I had the right answer with "fast" thinking for #3 though.
Note: When I say quickly & fast, I mean in less than a second, just the impulse answer. That is what fast thinking is I believe, but correct me if I am wrong.
These fast thinking problems rely on pattern recognition, so they will be easy if you have already seen the pattern, but you will fail if you apply the wrong pattern. Problem 3 tricks people who are used to everything being linear, which would probably be rather few people on HN.
I think the important skill is to be on the lookout, in your fast thinking, for problems which are slightly off. This is a clue that the pattern doesn't fit, and you should revert to slow thinking.
I quickly came up with the incorrect answers for #1 and #2, but was able to realize that something was wrong with them and thought about it for a few more seconds and got the right answers.
I had the right answer with "fast" thinking for #3 though.
Note: When I say quickly & fast, I mean in less than a second, just the impulse answer. That is what fast thinking is I believe, but correct me if I am wrong.