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Five lorries are parked in a French layby, having recently come off the ferry at Calais. The police know that the lorry headed for Lisbon is smuggling drugs, but they're not sure which one it is. All they have to go on is the following information.

  1. The Polish lorry came on the 6 o'clock ferry and is carrying coffee.
  2. The lorry in the middle is black.
  3. The British lorry came on the 9 o'clock ferry.
  4. The blue French lorry is somewhere to the left of the lorry carrying coffee.
  5. The lorry headed for Marseille is somewhere to the right of the lorry carrying potatoes.
  6. The Lithuanian lorry is headed for Nantes.
  7. The lorry carrying rice is next to the green lorry.
  8. The lorry headed for Genoa came on the 5 o'clock ferry.
  9. The Spanish lorry is somewhere to the right of the lorry headed for Marseille.
  10. The red lorry is headed for Hamburg.
  11. The white lorry is next to the Spanish lorry that came on the 7 o'clock ferry.
  12. The lorry carrying bread is at one of the ends.
  13. The black lorry came on the 8 o'clock ferry.
  14. The lorry carrying bread is next to the lorry carrying rice.
  15. The lorry headed for Hamburg came on the 6 o'clock ferry.

When the police arrive at the layby, which lorry driver should they arrest? I.e. should they raid the leftmost lorry, the second from the left, etc.?

Bonus question: which two possible lorries could be the one that's carrying tea?

In the spirit of teamwork, partial answers are acceptable.

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  • 1
    $\begingroup$ If they know the destination of the one carrying the drugs, couldn't they just check the bill of lading of each lorry? Surely this document would be required at any border crossing. $\endgroup$ – Ian MacDonald Jun 24 '15 at 11:36
  • $\begingroup$ Hmm, I guess you meant 'which one of two lorries could be carrying tea?'. $\endgroup$ – Bravo Jun 24 '15 at 11:39
  • $\begingroup$ @Bravo Well, only one lorry is carrying tea, but it could be either of two. I think "which two could be" is correct English? $\endgroup$ – Rand al'Thor Jun 24 '15 at 11:40
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    $\begingroup$ For Americans: a lorry is a truck and a lay-by is a rest area. $\endgroup$ – xnor Jun 24 '15 at 20:04
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    $\begingroup$ American police would arrest all the drivers and probably shoot their dogs too. After the dust settles a statement will be read to the innocents that will be vaguely similar to an apology but will not contain any actual words of apology nor will responsibility be accepted. A jury will award damages for wrongful arrest and no one in city hall will bat an eye over the incident. $\endgroup$ – Dean MacGregor Jun 24 '15 at 22:10
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Destination    Genoa     Hamburg    Nantes      Marseille   Lisbon
Origin         French    Polish     Lithuanian  British     Spanish
Colour         blue      red        black       white       green
Ferry Time     5 o'clock 6 o'clock  8 o'clock   9 o'clock   7 o'clock
Load           ?         coffee     ?           rice        bread

The police should raid the rightmost lorry.

Bonus: The French and Lithuanian lorries could be carrying tea.

EDIT:

This is how I deduced the answer. Using the facts that I knew, I created two sets of lorries, the first using the positional information to determine the known places.

(Ordered set)
Destination    
Origin         
Colour         (green)              black                   (green)
Ferry Time                          8 o'clock               
Load           (bread)   (rice)                 (rice)      (bread)

In the above, the bread load is at one of two ends (12) and rice is next to it (14), giving rise to two scenarios. The lorry carrying bread is green as it's next to the one carrying rice (7) and it can't be the one in the middle position as the middle lorry is known to be black (2) and it came on the 8 o' clock ferry (13).

In the second set, I used the remaining data to assign a set of possible characteristics to lorries.

(Unordered set)
Destination    Hamburg                         Nantes       Genoa      
Origin         Polish     British     French   Lithuanian              Spanish
Colour         red                    blue                              
Ferry Time     6 o'clock  9 o'clock                         5 o'clock  7 o'clock
Load           coffee    

The complete description of the Polish lorry is provided, barring the position (1,10,15). British lorry came in at 9 o'clock (3) and the French lorry is blue (4). The Lithuanian lorry is headed for Nantes (6) and the lorry to Genoa came in at 5 o'clock (8), while the Spanish lorry came in on the 7 o'clock ferry (11).

Looking at the second set, we can see that the nationality of the lorry to Genoa is the only one not known, but its time of arrival is known. There is only one other combination where both the nationality and time of arrival is missing, so I determined that the French lorry is headed to Genoa. Also, the timings for all are known except for the Lithuanian lorry, but I have the timing for the middle lorry, which is the one timing not accounted for.

(Updated ordered set)
Destination                         Nantes
Origin                              Lithuania
Colour         (green)              black                   (green)
Ferry Time                          8 o'clock               
Load           (bread)   (rice)                 (rice)      (bread)

(Updated unordered set)
Destination    Hamburg                Genoa          
Origin         Polish     British     French     Spanish
Colour         red                    blue                              
Ferry Time     6 o'clock  9 o'clock   5 o'clock  7 o'clock
Load           coffee   

At this point, I was hard pressed to decide on a position for the lorry with bread. Let's consider I picked the leftmost position, then rice would be in the lorry at the second position. The lorry headed to Genoa would occupy the fourth position as it has to be on the left of the lorry carrying coffee (4). This means the lorry to Hamburg will be in the fifth position.

(Updated ordered set, invalid)
Destination                         Nantes        Genoa      Hamburg
Origin                              Lithuania     French     Polish
Colour         green                black         blue       red   
Ferry Time                          8 o'clock     5 o'clock  6 o'clock          
Load           bread    rice                                 coffee

However, this would violate the condition that the lorry headed for Marseille is somewhere to the right of the lorry carrying potatoes (5), since potatoes can only be in the last three positions (other two have bread and rice) and there I've determined the locations are Nantes, Genoa and Hamburg.

So consider that the rightmost position is the lorry with bread, the lorry next to it has rice.

(Updated ordered set)
Destination    Genoa     Hamburg    Nantes      
Origin         French    Polish     Lithuanian  
Colour         blue      red        black                   green
Ferry Time     5 o'clock 6 o'clock  8 o'clock   
Load                     coffee                 rice        bread

(Updated unordered set)
Destination                
Origin         British     Spanish
Colour                     
Ferry Time     9 o'clock   7 o'clock
Load              

So Marseille can be the destination for either of the lorries at the right end, as potatoes can only be in the middle lorry or the leftmost one (5). Now only the colour of the fourth lorry is unknown, and I know that there is a white lorry next to a Spanish lorry (11). This makes the fourth lorry white, the fifth lorry is Spanish and coming in at 7 o'clock, while the fifth lorry is British coming in at 9 o'clock. Also, the Spanish lorry is somewhere to the right of the lorry headed for Marseille (9), which means the fourth lorry is going to Marseille, while the fifth is headed to Lisbon.

Destination    Genoa     Hamburg    Nantes      Marseille   Lisbon
Origin         French    Polish     Lithuanian  British     Spanish
Colour         blue      red        black       white       green
Ferry Time     5 o'clock 6 o'clock  8 o'clock   9 o'clock   7 o'clock
Load                     coffee                 rice        bread

With that the solution is complete, with no more data available to firmly establish which lorry carries potatoes, so either the blue or black one could be carrying tea, the other commodity we haven't been given any information about.

This may not be the most efficient way to explain (or even solve), but this is the best way I can explain what I did to reach the solution.

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  • 6
    $\begingroup$ Perfect solution! But could you add an explanation of your logic? These puzzles are fun to solve, and it's even fun to work through a full answer, but just seeing the solution isn't much fun on its own... $\endgroup$ – Rand al'Thor Jun 24 '15 at 11:37
  • $\begingroup$ This is brilliant! You weren't the first to post the answer (though you were the first to get the bonus question right), nor were you the first to add an explanation (though I like your explanation better than KritixiLithos's), so I'm going to accept this answer :-D $\endgroup$ – Rand al'Thor Jun 25 '15 at 10:10
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From left to right, the lorries are:

1) Blue French lorry that arrived on the 5'o clock ferry and is travelling to Genoa.
2) Red Polish lorry that arrived on the 6'o clock ferry and is travelling to Hamburg, carrying coffee.
3) Black Lithuanian lorry that arrived on the 8'o clock ferry and is travelling to Nantes, carrying potatoes.
4) White British lorry that arrived on the 9'o clock ferry and is travelling to Marseilles, carrying rice.
5) Green Spanish lorry that arrived on the 7'o clock ferry and is travelling to Lisbon, carrying bread.

The police must nab the driver of the rightmost lorry. Atacar a los españoles!

Bonus question: The French and Polish lorries could be carrying coffee and tea; perhaps that's why they are adjacent to each other ;)

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  • 1
    $\begingroup$ This is correct (except that you don't know whether it's the French or Lithuanian lorry that's carrying potatoes), but could you add an explanation of the logic you used? $\endgroup$ – Rand al'Thor Jun 24 '15 at 11:33
  • $\begingroup$ @randal'thor: It is just logical deduction, right? Fitting all statements together :) Was not sure how to explain the answer, without being verbose. $\endgroup$ – Bravo Jun 24 '15 at 11:37
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    $\begingroup$ Yes, it's just logical deduction, but that's the whole point of the puzzle! If you don't include your reasoning, how do I know you didn't just find the same puzzle in a book or on the internet? :-) Reading a fully explained solution of this sort of puzzle is almost as much fun as solving it, but just reading the answer won't be satisfying for anyone else. And verbosity is fine - if people can't be bothered to read it (their loss), they can just read the summarised solution that you've already put. $\endgroup$ – Rand al'Thor Jun 24 '15 at 11:40
  • $\begingroup$ I was going to make the joke about how it can't be the Lithuanian truck carrying potatoes because there is no potato, only sadness, when I realized that was the Latvian truck... $\endgroup$ – Michael Jun 24 '15 at 20:11
  • $\begingroup$ It is interesting to post your deduction especially when you don't find the same result ;) Otherwise, it has no point, this is only straightforward deduction. I found that Polish lorry is coffee only, the French can carry tea or potatoes as the Lithuanian one. $\endgroup$ – Poutrathor Jun 25 '15 at 11:42
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The answer is as such:

Origin      | French | Polish  | Lithuanian  | British   | Spanish |
Destination | Genoa  | Hamburg | Nantes      | Marseille | Lisbon  |
Ferry Time  | 5      | 6       | 8           | 9         | 7       |
Colour      | blue   | Red     | Black       | White     | Green   |
Goods       | ?      | Coffee  | ?           | Rice      | Bread   |

Here is the explanation. We start from a list of possibilities which soon narrow down into specific details.

The possibilities start with:

Origin      | PBFLS | PBFLS | PBFLS | PBFLS | PBFLS |
Destination | MNGHL | MNGHL | MNGHL | MNGHL | MNGHL |
Ferry Time  | 56789 | 56789 | 56789 | 56789 | 56789 |
Colour      | BbGWR | BbGWR | BbGWR | BbGWR | BbGWR |
Goods       |TTCPRB |TTCPRB |TTCPRB |TTCPRB |TTCPRB |

Clues 2 & 13 lead us to that the middle lorry is black and came on the 8 o' clock ferry. Clues 1 & 3 & 4 & 11 further say that The middle truck is not British nor French nor Spanish nor Polish because of the ferry time and colour; and it does not carry coffee. Clues 8 & 10 say that the middle truck is not headed for Genoa or Hamburg for the same reason. Clues 12 & 14 say that the middle lorry cannot possibly be carrying bread or rice because it is in the middle. After putting all this information together, we can see that the middle truck is Lithuanian and using clue 6 we know that it is headed for Nantes.

Origin      | PBF S | PBF S |   L   | PBF S | PBF S |
Destination | M GHL | M GHL |   N   | M GHL | M GHL |
Ferry Time  | 567 9 | 567 9 |   8   | 567 9 | 567 9 |
Colour      |  bGWR |  bGWR |   B   |  bGWR |  bGWR |
Goods       | TCPBR | TCPBR |   TP  | TCPBR | TCPBR |

Clues 12 & 14 say that bread can only be at one of the ends and that rice must not be at the ends. Clue 4 says that the coffee lorry cannot be at the left end and that the blue French lorry cannot be at the right most end. Clue 5 says that the right end cannot be having potatoes and the left end cannot be headed to Marseille. Clue 7 says that the green lorry cannot be having rice. Clue 9 & 11 says that the first two lorries from the left cannot be Spanish or have the time as 7 o' clock because the Spanish lorry came on 7 o' clock. Clue 9 also tells us that the Spanish lorry is not headed towards Marseille.

Origin      | PBF   | PBF   |   L   | PBF S | PBF S |
Destination |   GHL | M GHL |   N   | M GHL |   GHL |
Ferry Time  | 56  9 | 56  9 |   8   | 567 9 | 567 9 |
Colour      |  bGWR |  b WR |   B   |  b WR |  bGWR |
Goods       | TCPB  | TCP R |   TP  | TCP R | TC B  |

Clues 1 & 10 & 15 give us all the information on the Polish lorry except for its position. Clues 1 & 4 say that the Polish lorry cannot be on the left most and the French one cannot be on the right most.

Origin      |  BF   | PBF   |   L   | PBF S | PB  S |
Destination |   G L | M GHL |   N   | M GHL |   GHL |
Ferry Time  | 5   9 | 56  9 |   8   | 567 9 | 567 9 |
Colour      |  bGW  |  b WR |   B   |  b WR |  bGWR |
Goods       | T PB  | TCP R |   TP  | TCP R | TC B  |

Now I am going to forget the positions of the lorries and we are left with.

Origin      |   P   |   B   |   L   |   F   |   S   |
Destination |   H   |       |   N   |       |       |
Ferry Time  |   6   |   9   |   8   |       |   7   |
Colour      |   R   |       |   B   |   b   |       |
Goods       |   C   |       |   ?   |       |       |

Clue 8 says that the lorry headed for Genoa came on the 5 o' clock ferry. The only lorry with no time is the French lorry and we will fill that out. Clue 11 says that the Spanish lorry cannot be white. And then we can see that Spanish is green.

Origin      |   P   |   B   |   L   |   F   |   S   |
Destination |   H   |       |   N   |   G   |       |
Ferry Time  |   6   |   9   |   8   |       |   7   |
Colour      |   R   |   W   |   B   |   b   |   G   |
Goods       |   C   |       |   ?   |       |       |

Now reflecting back on our original grid, we see that Spanish only fits with the last one. Clue 11 helps us find out the second-rightmost lorry. After cancelling out the Spanish (S) from the origin of the first two lorries, we see that the lorries are French and Polish. We can see that Marseille can only fit with the British Lorry.

Origin      |   F   |   P   |   L   |   B   |   S   |
Destination |   G   |   H   |   N   |   M   |   L   |
Ferry Time  |   5   |   6   |   8   |   9   |   7   |
Colour      |   b   |   R   |   B   |   W   |   G   |
Goods       | T PB  |   C   |   TP  | T P R | T  B  |

Clue 5 tells us that the Marseille lorry does not have potatoes. Clue 7 tells us that the British lorry is carrying rice. According to clue 14 the Spanish lorry carries bread. We are finished with:

Origin      |   F   |   P   |   L   |   B   |   S   |
Destination |   G   |   H   |   N   |   M   |   L   |
Ferry Time  |   5   |   6   |   8   |   9   |   7   |
Colour      |   b   |   R   |   B   |   W   |   G   |
Goods       |  TP   |   C   |   TP  |   R   |   B   |

Finally

The answer to the first question is that the police should arrest the Spanish driver as he is headed to Lisbon. Both the French and the Lithuanian lorries have a possibility of carrying Tea.

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  • $\begingroup$ Ah, finally an explanation! :-D I haven't got time to go through all this now, but it's looking good. (Hint: you may find it useful to write down which origin, destination, etc. correspond to each other before finding out where they go. When I wrote out a solution, the left-to-right positions were the very last thing I solved.) $\endgroup$ – Rand al'Thor Jun 24 '15 at 14:09

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