One idea I would suggest is to write a list with all the combinations down (i.e blue smooth square etc.) and go through the rules to start eliminating those that aren't allowed in the final 4.
Don't, I am absolutely shocked that I got it right! I actually tried the puzzle for like half an hour yesterday and got nowhere. I came back to it today with a fresh mind and was able to do it in just a few minutes! I can't believe I got it.
That's what I tried to do and that's when I ended up finding the contradiction and then the whole attempt just collapsed.
It doesn't look like any more guesses are coming. So here is the answer to this week's puzzle... I have: a furry yellow circle, a smooth green square, a smooth red circle, and a furry red circle. I believe the most effective method of solution here is as SilentP suggested, to write down the 27 possible objects and eliminate them in batches by seeing which objects are forbidden by each rule in turn. You end up with a few possibilities remaining. To select from these, you can apply the "all colours" rule to determine the two yellow and green shapes, and then the "circles>smooth" rule to determine the two red shapes. Also notice in the opening sentence that all four of my objects must be different Thank-you to all who took part. We look forward to your joining in next week's puzzle, which I won't be hosting.
Looking forward to next week! I made a sort of coordinate system to eliminate the impossible ones. So, were the answers listed randomly or did everyone guess the green one first?
In all honesty, I usually consider myself pretty good at these sorts of puzzles, but tried yesterday for a few minutes and gave up after I got light-headed.
I started with the contradiction, knowing that there were no rough shapes. Then I listed each of the three colors and figured out what shapes they had to be based on the rules. A couple of them had to be smooth based on this info, so at least 3 of the objects had to be circles. For the last shape that could have been any color there were two possibilities, and since the question stated all the objects were different there was really only one choice. I actually tried writing it out methodically on the first day, but as I mentioned before that got me nowhere. So after that I just tried doing it in my head and it seemed to work better for some reason.
I know he doesn't pop back and chat, but it would be interesting to know Jim Gamma's method since he solved it so quickly
The more natural way of solving the puzzle is to take one property, like triangles, and see what you can deduce about triangle objects. You will get some specific facts: "triangles will always be smooth." In fact, there are 5 relatively simple deductions you can make: triangles -- must be smooth and red squares -- must be smooth green -- must be square and smooth yellow -- must be circle and furry rough -- cannot exist Once you get to that stage, it is not hard to solve.
When I was testing your puzzle last week, I ended up using the SilentP method of determining all possibilites in a table (a.k.a. the Guess Who? method), then going through each rule one by one, eliminating the impossible, thus interpreting whatever remains, however improbable, as the truth.