Each time you visit the NRICH site there will be some activities which are 'live'. That means we are inviting you to send us your solutions and we will publish a selection of them, along with your name and your school's name. If you'd like to know more about what we're looking for, read this short article.
The last day for submitting solutions to these live problems is Monday 27 November.
problem
Charlie's delightful machine
Age
11 to 16
Challenge level
Here is a machine with four coloured lights. Can you develop a strategy to work out the rules controlling each light?