problem Squaring the Circle and Circling the square Age 14 to 16 Challenge level If you continue the pattern, can you predict what each of the following areas will be? Try to explain your prediction.
problem Binary Squares Age 16 to 18 Challenge level If a number N is expressed in binary by using only 'ones,' what can you say about its square (in binary)?
problem Circles ad infinitum Age 16 to 18 Challenge level A circle is inscribed in an equilateral triangle. Smaller circles touch it and the sides of the triangle, the process continuing indefinitely. What is the sum of the areas of all the circles?
problem Converging Product Age 16 to 18 Challenge level In the limit you get the sum of an infinite geometric series. What about an infinite product (1+x)(1+x^2)(1+x^4)... ?
problem The Amazing Splitting Plant Age 5 to 7 Challenge level Can you work out how many flowers there will be on the Amazing Splitting Plant after it has been growing for six weeks?
problem Magic Plant Age 5 to 7 Challenge level On Friday the magic plant was only 2 centimetres tall. Every day it doubled its height. How tall was it on Monday?
problem The Great Tiling Count Age 7 to 11 Challenge level Compare the numbers of particular tiles in one or all of these three designs, inspired by the floor tiles of a church in Cambridge.
article Sum the Series This article by Alex Goodwin, age 18 of Madras College, St Andrews describes how to find the sum of 1 + 22 + 333 + 4444 + ... to n terms.
interactivity Proof Sorter - Geometric Sequence Can you correctly order the steps in the proof of the formula for the sum of the first n terms in a geometric sequence?
problem Pocket money Age 11 to 14 Challenge level Which of these pocket money systems would you rather have?