20 minutes. Up to 10 questions.

Find the rule behind a row of numbers and work out which number comes next. You can go back to earlier questions until the timer runs out. Candidates score 80% correct on average.

• • Start with the differences between consecutive numbers
• • If that fails, look at ratios, squares, or two series interleaved
• • Check your rule against the whole series, not just the last step
• • Every question is explained afterwards, right or wrong.