A shopkeeper records 12, 4, 7, 20 and 9 sales on five days. What is the median number of sales?

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Ordering the five daily totals gives 4, 7, 9, 12 and 20, and the central one of the five positions holds 9, so the median is 9 sales. Answering 7 sales takes the entry standing in the middle of the unordered record, which sits there only because of the sequence in which the days were written down.