If you haven’t heard about this riddle before then you should try solve it yourself first. It’s a lot easier than you think. Most web sites post it with huge notices that Einstein himself said that 98% of the population would not be able to solve it. Well, this could have been true in his time, since about 98% of the population would not have a chance to read the riddle in a first place, but now with the power of the interwebbies you can read and solve it too. It’s not really hard, if I could do it in under 15 minutes – so could anyone else.
I am posting the rules the way I found them on the internet – this way you can get hyped up about 2% vs. 98%.
ALBERT EINSTEIN’S RIDDLE
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 good luck and don’t give up.
1. In a street there are five houses, painted five different colours.
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.
THE QUESTION: WHO OWNS THE FISH?
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 next to, and 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 centre house drinks milk.
9. The Norwegian lives in the first house.
10. The man who smokes Blends lives next to the one 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 neighbour who drinks water.
The solution is under the cut. I encourage you (again!) to try and solve it yourself before you look there.
First – we build a table with all the information we know so far. Of course, some hints will not fit this table, so we will add them below in a form of inter-dependencies.
We will list other hints in a similar fashion (see picture below). Note, that some of the hints, like The man who smokes Blends lives next to the one who keeps cats are hard to depict like that, but the least we can do at the moment is note that man who smokes Blends DOES NOT own cats 🙂 So we will put these hints as negating hints. Note the minus sign in notation.
Note that we have already started solving this riddle. Look at the third line – we already know that owner of the yellow house smokes Dunhill AND does not own horses. That’s the way we will be solving this problem – by eliminating all the impossible scenarios.
One last thing we need to do (and it’s the messiest one) is to figure out the sequence of the houses. We need this step to use the information about who’s neighbour with whom later on. Since Norwegian lives in the first house (hint 9) AND he lives next to blue house (hint 14) we can establish that BLUE house is second down the street. Additionally, hint 4 tells us that GREEN and WHITE house are next to each other and GREEN is on the left. Since the two cannot fit to the left of the blue (there’s only one house where Norwegian lives), those two are to the right. Which gives us following combinations:
We have ignored a few hints so far, but don’t worry – we’ll get to them later. Next step in solving this would be to put all negating hints from other two tables into the first table. Let’s start with Brit – since he owns the red house he can’t be drinking coffee (it’s Green house owner’s prerogative) and can’t smoke Dunhill (it belongs to Yellow house). Using the same approach we can say that Swede doesn’t smoke Pall Mall (since he owns dogs). German, by the same rationale, isn’t drinking beer, since beer is tied in with Blue Master cigars. He also doesn’t own birds, since birds belong to Pall Mall smoker. Dane isn’t smoking Blue Master (tied to beer) and his house isn’t green (tied to coffee), since he drinks tea.
One more additional step here: to make sure we capture all impossible combinations, let’s note that since Brit owns red house – no one else can have red, no one except Dane can drink tea and so on. The result is the table below.
See, it’s getting better! From step 3 we know that green and white houses are to the right of the blue (which is a second house on the street). This means that Norwegian, who lives in the first house, cannot live in neither one of them. Let’s add that to the table too. WAIT! We have just eliminated four out of five colors! OMG! NORWEGIAN LIVES IN YELLOW HOUSE! WE SOLVED THE FIRST STEP! OMG!!! But let’s not stop here. Look at the step 2 – we already know that owner of the yellow house smokes Dunhill and doesn’t own neither horses (hints 7,11) nor birds (hint 6) . Let’s add that too and see what’s going on.
Now look back at the step 3 – since we know that first house is yellow it leaves us with only two possible combinations:
From the hint 8 we know that man who lives in the middle house drinks milk. Now, from the only two possibilies left the middle house is either green or red. But the owner of green house drinks coffee (hint 5). That leaves only one possible combination – second line on the picture above. This means that the house in the middle is a red one, Brit lives here and he drinks milk. For the sake of conserving space, let’s put the table together with house sequence in the following image:
Now let’s look at our Norwegian friend again, since he’s the most telling. He smokes Dunhill, therefore he doesn’t drink beer. He also doesn’t drink coffee, since coffee belongs to the green house and he lives in yellow. This leaves out only one drink – water. Let’s put that into table and eliminate water from everybody else. Would you look at THAT! German’s DRINK column is now eliminating 4 possible choices leaving him with just COFFEE! But this immegiately means that German lives in the GREEN house (hint 5)! Oh, look again! Poor Swede is left with only one choice remaining for drinks – BEER! Which automatically makes him smoke Blue Master! Do you see how pieces fall into places almost all by themselves?
Now let’s eliminate all the pieces we have assigned already from the rest of the choices. So far we know everyone’s tastes in drinks and we know exactly how houses line up on the street. Let’s look at hint 15 – the man who smokes blends has a neighbour who drinks water, who is Norwegian. But Norwegian has only one neighbour who owns a blue house. This means no other house can have Blends, so let’s eliminate it from those houses we have already established – German, Brit and Norwegian. But we already know what German and Norwegian smoke, so that leaves us with just eliminating Blends from the Brit. This leaves only one possible choice of cigars and that is Pall Mall. This means our Brit friend fancies birds. Let’s note all these facts in our table. Notice that now we know everything about the Brit – or the Red house.
Now let’s look at the hint 10. There are two neighbours to the man who smokes Blends (and lives in a Blue house) who might own cats – Brit and Norwegian. But since we have already established that Brit owns birds, this leaves Norwegian with Cats. Note that we now have full view on Norwegian as well – and about the Yellow house.
We are almost done! hint 11 tells us that whoever lives next to man who smokes Dunhill (who is Norwegian) keeps horses. There’s only one neighbour to the Norwegian and that is a man in a Blue house. This means no other house can have horses, so let’s eliminate that from the German’s list. This leaves him with only one possible alternative – FISH! Problem solved!
But let’s see what else we can establish. Since German owns the fish this means Blue house owner has the horses which makes him Dane. The only unidentified house owner left on the street is Swede which means he owns White house. So let’s clean up our table from all the intermediary notes and just leave the clean solution: