Carlton Kids £9.99
Split in three levels (Starters, intermediate and advanced) there are over 240 puzzles and in each section you will find ones that seem easy and others fiendish. Most are of the what number comes next or what would the next variant of a picture be. Just now and again there is a text question.
You will need to know your basic maths and apply logic to overcome these but given time and patience you should crack most of these. There is, of course an answers section at the rear and it does explain how the answer was arrived at. Knowledge of prime numbers is amust and square roots as well.
This is aimed at children, but parents will find plenty of challenges here too.