DS1 is in year 7 and recently obtained a gold certificate in the junior maths challenge. I was pretty impressed, and decided to have a go myself to see how hard it was. Turns out it's not actually that hard 
Anyone else up for it? The link is below, you can't spend more than an hour on it and read the mark scheme before you start, as you can lose marks for answering the later questions incorrectly.
www.mathcomp.leeds.ac.uk/b_file.php?id=381
Go on- give it a try?