A cubic storage unit is designed such that its side length, x x\,x meters, is an integer. An engineer claims that if the volume of the unit, V=x3V = x^3V=x3, is a multiple of 3, then the side length x x\,x must be a multiple of 3. Use proof by contradiction to prove that the engineer's claim is correct.
107 exam-style questions on AQA A Level Maths 1.4.1 Structure and methods of proof. Each one has a worked solution and a mark scheme showing where the marks go.