Can you crack these very difficult challenge ciphers? How might you systematise the cracking of unknown ciphers?

How can you quickly sort a suit of cards in order from Ace to King?

Can you interpret this algorithm to determine the day on which you were born?

What day of the week were you born on? Do you know? Here's a way to find out.

Imagine a strip with a mark somewhere along it. Fold it in the middle so that the bottom reaches back to the top. Stetch it out to match the original length. Now where's the mark?

Is the regularity shown in this encoded message noise or structure?

A sequence of numbers x1, x2, x3, ... starts with x1 = 2, and, if you know any term xn, you can find the next term xn+1 using the formula: xn+1 = (xn + 3/xn)/2 . Calculate the first six terms of this. . . .

This article explains the concepts involved in scientific mathematical computing. It will be very useful and interesting to anyone interested in computer programming or mathematics.

Can you think like a computer and work out what this flow diagram does?

However did we manage before calculators? Is there an efficient way to do a square root if you have to do the work yourself?

It's like 'Peaches Today, Peaches Tomorrow' but interestingly generalized.

When in 1821 Charles Babbage invented the `Difference Engine' it was intended to take over the work of making mathematical tables by the techniques described in this article.

Vedic Sutra is one of many ancient Indian sutras which involves a cross subtraction method. Can you give a good explanation of WHY it works?

How would you judge a competition to draw a freehand square?

Scheduling games is a little more challenging than one might desire. Here are some tournament formats that sport schedulers use.

Keep constructing triangles in the incircle of the previous triangle. What happens?