A short introduction

Complex Problems

The puzzles are marked with stars (*) that show the degree of difficulty of the given puzzle.
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Copyright © 1996-2011. RJE-productions. All rights reserved. No part of this website may be published, in any form or by any means, without the prior permission of the authors.

Eight Queens ***

Queen!
This is a commonly known chess problem...
The Question: In how many ways can you arrange 8 queens on a standard chess-board in such a way that none of them is attacking any other?
The Answer: Click here!...

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Names & Numbers ***

Names and Numbers
Thanks to Mike and Ruth VanderMeer from Canada, we can present you the following names and numbers puzzle:

Four words add up to a fifth word numerically: 

     mars
    venus
   uranus
   saturn
  -------- +
  neptune
Each of the ten letters (m, a, r, s, v, e, n, u, t, and p) represents a digit in the range 0 up to 9 (equal letters represent equal digits and different letters represent different digits). Furthermore, the digits 1 and 6 are being used most frequently.
The Question: What number does neptune represent?
The Answer: Click here!...

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Nineteen Numbers Net ***

Fill this net with nineteen numbers!
This is the toughest number net on our site! It has nineteen circles that have to be filled with the numbers 1 up to (and including) 19. These numbers have to be placed in such a way that all numbers on any horizontal row and any diagonal line add up to the same sum.

Warning: there are many horizontal and diagonal lines, which have a different number of circles (3, 4, or 5), nevertheless all these sums have to be equal!

The Question: How should the nineteen numbers be placed in the net?
The Answer: Click here!...

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Cash for a Car ***

Thanks to Lucas Jones we can present you the following puzzle:

A man is going to an Antique Car auction. All purchases must be paid for in cash. He goes to the bank and draws out $25,000.

Since the man does not want to be seen carrying that much money, he places it in 15 envelopes numbered 1 through 15. Each envelope contains the least number of bills possible of any available US currency (for example, no two tens instead of a twenty).

At the auction he makes a successful bid of $8322 for a car. He hands the auctioneer envelopes 2, 8, and 14. After opening the envelopes the auctioneer finds exactly the right amount.

The Question: How many ones did the auctioneer find in the envelopes?
The Answer: Click here!...

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Ladder Alley ***

Ladder
In an alley two ladders are placed cross-wise. The lengths of these ladders are resp. 2 and 3 meters. They cross one another at one meter above the ground.
The Question: What is the width of the alley?
The Answer: Click here!...

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Cat & Mouse ****

Cat and Mouse!
Four white pieces (the mice) are placed on one side of a chess-board, and one black piece (the cat) is placed at the opposite side. The game is played by the following rules:
  • Black wins if it reaches the opposite side.
  • White wins if it blocks black in such a way that black can not make any move anymore.
  • Only diagonal moves (of length 1) on empty squares are allowed.
  • White only moves forward.
  • Black can move backward and forward.
  • Black may make the first move, then white makes a move, and so on...
The Question: Is this game computable (i.e. is it possible to decide beforehand who wins the game, no matter how hard his opponent tries to avoid this)?
The Answer: Click here!...

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Car Parking *****

Cars parked in a street.
A street of length L is randomly filled with cars (one by one), where the length of a car is the unity of L (i.e. 1).
The Question: What is the expectation for the number of cars that can be parked until the street is filled?
The Answer: Click here!...

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Copyright © 1996-2011. RJE-productions. All rights reserved. No part of this website may be published, in any form or by any means, without the prior permission of the authors.