Year 1987- Volume 23
2020 - Present

Greetings to our Readers! First of all I would like to draw your attention to some changes in our journal.

Peter Donovan

It is not easy to construct chess positions in which it is rational to advance a pawn to the eighth rank and promote it to a rook, knight or (especially) a bishop.

Gavin Brown

Have you ever cast a second glance at the ten digit codes now found on most books? A random volume from my bookshelf carries the message

ISBN 0140050930.

Lew Havercamp and John Loxton Architecture and geometry are old friends. Often architects borrow interesting shapes from geometers, but traffic in the other direction is less frequent.

Q.696 $k$ is a whole number. There is a pile of $N$ coins shared amongst $n$ brigands as follows:

Q.672 Find the least natural number whose last digit is 6 such that it increases by the factor 4 when this last digit is carried to the beginning of the number

Q.684 $B\stackrel{^}{A}C$ is an obtuse angle. A circle through $A$ cuts $AB$ at $P$ and $AC$ at $Q$.

R. Grimshaw

One of the more fascinating and unexpected discoveries of modern mathematics is the soliton.

Cheryl E. Praeger

I hope that girls reading the title have already retorted: "Why shouldn't she if she wants to!"

Peter Donovan

This note is a sequel to the article on underpromotions in chess published in the previous issue of Parabola.

In Randwick, the cats, I declare,
They number one third of a square,
If a quarter did roam,
Just a cube would stay home.
How many, at least, must be there?

Q.696 $k$ is a whole number. There is a pile of $N$ coins shared amongst $n$ brigands as follows:

Q.708 A four digit number $abcd$ has the property that $a+b=c×d$ and also $a×b=c+d$. Find all possibilities.

John Murray

Going from one place to another can be a difficult problem.

Bill McKee Have you ever wondered how your calculator or computer finds quantities such as $\mathrm{sin}\left({63}^{\circ }\right)$ or $\mathrm{tan}\left({17}^{\circ }\right)$ ?

In a recent edition of Mathematical Spectrum (the English equivalent of Parabola) the following famous problem was discussed:

Q.720 When the initial digit of a whole number $x$ is deleted, the number decreases by a factor of 13. Find all possible values of $x$.

Q.708 A four digit number $abcd$ has the property that  $a+b=c×d$ and also $a×b=c+d$. Find all possibilities.