Error message

Warning: "continue" targeting switch is equivalent to "break". Did you mean to use "continue 2"? in require_once() (line 341 of /home/n9esbwprkar5/public_html/domains/circles/includes/

Can you arrange a set of numbers in pairs, so that the sum of each pair is a perfect square? What if the sums must be primes? What if the sums must all be distinct? Discover the surprising variations in this simple challenge.

02/28/2017 - 16:40

Every journey has its costs and its rewards. Can you complete this one without any debt?

02/28/2017 - 16:49

A twist on the game of Dots and Boxes – but instead of capturing as many squares as possible, you and your opponent are going after gold doubloons!

02/26/2017 - 02:46

In Evenland, the citizens never invented the number one; instead, they started with 2, and built up sums and products from that starting point. What can we say about prime numbers in Evenland?

02/24/2017 - 17:49

Cook up some polyhedrons by following simple recipes. Invent your own recipes, too!

02/28/2017 - 16:01

This fleshed out activity based upon the John Conway game "Brussels Sprouts" teaches the game and then provides a teacher's guide for leading further investigations.

07/30/2018 - 16:54

In how many ways can you draw a star using all the vertices of a polygon, without lifting your pencil from the paper? Are there some polygons for which it's not possible?

02/24/2017 - 17:53

Use specially shaped blocks to “stomp out” dots on a grid of squares. But if you stomp on a square without a dot, a new one appears! Can you stomp out all the dots?

02/26/2017 - 02:48

Can you see the light? That is, can you see the patterns in light bulbs that are left on, after repeatedly following a simple rule to switch them on and off?

06/02/2017 - 07:25

The rules for this classic game are very simple: The player who removes the last object (from two or more initial piles of objects) wins. But is a winning strategy that simple?

02/28/2017 - 15:38