Got this from Jem, and answered it too. But I’m posting my solution here because when I googled to check if I got it right, I saw much simpler/faster ways to answer it hahaha which made me kinda sad that I took a “logical-long-cut.” But nonetheless, it was nice to know that I solved it either way.

Are you in the TOP 2% of intelligent people in the world? Solve the riddle and find out. There are no tricks, just pure logic. So goodluck and don’t give up. 1. In a street there are five houses, painted five different colors. 2. In each house lives a person of different nationality. 3. These five homeowners each drink a different kind of beverage, smoke different brand of cigar and keep a different pet.

QUESTION: WHO OWNS THE FISH?

Hints: 1. The Brit lives in a red house. 2. The Swede keeps dogs as pets. 3. The Dane drinks tea. 4. The Green house is on the left of the White house. 5. The owner of the Green house drinks coffee. 6. The person who smokes Pall Mall rears birds. 7. The owner of the Yellow house smokes Dunhill. 8. The man living in the center house drinks milk. 9. The Norwegian lives in the first house. 10. The man who smokes Blends lives next to the man who keeps cats. 11. The man who keeps horses lives next to the man who smokes Dunhill. 12. The man who smokes Blue Master drinks beer. 13. The German smokes Prince. 14. The Norwegian lives next to the Blue house. 15. The man who smokes Blends has a neighbor who drinks water.

Albert Einstein wrote this riddle during the 19th century. He said that 98% of the population would not be able to solve it.

My method was to represent each house, and list down all possibilities in each house… and do a process of elimination. But I would have to say that the solution I found in Google after the excercise, was a faster and more elegant attack on the problem.

Though my method was far from efficient, I guess I could find solace in the fact that I thought out of the box hahaha.

In my method, after filling up the “possibilities” from the conditions on all 5 houses, and got something that looked like this. The little letter prefixes on some “possibilities” are only indicators – so when I eliminate something that is paired with another condition, I won’t forget to delete it’s “partner.”

Getting right to it, you’ll notice that Conditions 9 and 13 forces the Norwegian and German to be distinct entries, just like the others¹. Furthermore, the GERMAN/PRINCE pair eliminates the other cigars from the German’s entry… namely: BEER/BLUEMASTER, YELLOW/DUNHILL, BIRDS/PALLMALL, and BLENDS

Condition 14 states that the second house should be blue – the German, Dane and the Swede are now in the running for the 2nd house.

Condition 4 and 14 make it impossible for the Norwegian’s house to be blue, green, or white. It could’ve been green if the 2nd was white, which it can’t be (blue remember?). Eliminating the BLUE, GREEN, and WHITE adds YELLOW/DUNHILL as the Norwegians fixed values.

We now take out the extraneous relationships GREEN/COFFEE, BIRDS/PALLMALL, BEER/BLUEMASTER, and BLENDS. Also, take out YELLOW/DUNHILL from everyone else.

Condition 8 allows us to take milk out from the Norwegian Dude… which leaves him with WATER – and in turn eliminates it from everyone else.

Condition 15 allows us to eliminate BLUE from the German, and eliminate him altogether as a possible 2nd house – because it says the man who smokes Blends should be beside the Norwegian water-drinker.

We also know that of the three (German, Dane and Swede), they could also be green or white, therefore 2 of the three have to be adjacent. This puts the Brit (RED) either as the center or the last house. If you notice, the 2 possible milk drinkers left are the Swede and the Brit, so the German is now solidified as the 4th house.

The reason for such logic is that the possible permutations are:

1. SWEDE as BLUE, BRIT as center, GERMAN as GREEN, and DANE as WHITE last
2. DANE as BLUE, BRIT as center, GERMAN as GREEN, SWEDE as WHITE last
3. DANE as BLUE, SWEDE as GREEN center, GERMAN as WHITE, and BRIT as last

The Dane can never be the center house since he ain’t a milk drinker, nor can he be green. So the 4th permutation of SWEDE as BLUE, DANE as GREEN center GERMAN as WHITE and BRIT as last – will not work.

We also know that the BLUE house is the man with horses, because the man that smokes Dunhill is already the first house (condition 11) – so the Swede’s pet dogs will not allow him to be the blue house. Having said that, the Dane is now the blue, house with horses for certain! So take out WHITE, CATS, FISH, and BIRDS/PALMALL from the Dane – and we’re now left with a person who smokes BLENDS.

You’d notice at this point, only one person can possibly be a BLUEMASTER/BEER smoker/drinker (Swede), so we can now delete GREEN/COFFEE and MILK from the Swede (making his house WHITE in the process)

If we eliminate BLUEMASTER from the rest, then we see the Brit as a PALMALL smoking, BIRD owner (taking condition 6 into account). Not only that, it leaves the Brit as the milk drinker – ergo the center house.

I guess condition 10 was talking about the Norwegian as the cat-dude.

So we take out CATS, HORSES, FISH from the Brit… and HORSES and FISH from the Norwegian.

And since we have derived enough to finish the process of cross-elimination, we can see that the Swede has to be the last, white, house for the German GREEN house to be on its left.

Houses are now:

1. NORWEGIAN/YELLOW/CATS/WATER/DUNHILL
2. DANE/BLUE/HORSES/TEA/BLENDS
3. BRIT/RED/BIRDS/MILK/PALLMALL
4. GERMAN/GREEN/FISH/COFFEE/PRINCE
5. SWEDE/WHITE/DOGS/BEER/BLUEMASTER

So my final answer is: the NAZI owns the fish!