Eight pupils read 15, 3, 9, 1, 12, 6, 20 and 7 pages. What is the median number of pages? Enter the number of pages.

Explication

Sorted by size, the eight counts run 1, 3, 6, 7, 9, 12, 15 and 20, and the two central positions of eight hold 7 and 9, whose mean is 8 pages. Averaging the pair that stand in the middle of the list as recorded, 1 and 12, gives 6.5 instead, because that pair was never ranked by size.