Each question in this set shows a series of numbers with a question mark standing in for the missing number. Look carefully at the numbers you are given and work out the rule connecting them: it could be a fixed amount added or taken away each time, a fixed multiplier or divisor, a gap between the numbers that grows or shrinks by a steady amount, two separate series running through the same list one term at a time, or a rule that builds each number from the two numbers just before it. Once you have spotted the rule, pick the option, A to E, that carries the series on correctly. Exactly one option fits in each question; the other four are built around mistakes that are easy to make, such as using the wrong step size, stopping a growing gap one step too soon, or losing track of which of two interleaved series you are following. Look at the worked example first, then answer the questions in order - they begin gently and become more demanding as the set goes on.