The ultimate lateral-thinking challenge. If you relish a serious mental workout, this collection of 100 brain teasers will demand your very best lateral thinking skills and mathematical rigour to solve. These puzzles will amuse and perplex in equal measure. But do not worry, full, detailed solutions are found at the back of the book so you can get into the head of these fiendish setters! These mental puzzles require serious application, imagination and skill to solve. Some demand a logical approach, others a methodical, mathematical mind. Are you up to the challenge of solving these rigorous but entertaining mathematical puzzles? Gold title * From Collins, the the UK's No.1 puzzles publisher * Selected by Sunday Times Puzzles Editor John Owen * Challenging lateral thinking puzzles with fully-worked solutions.