Eight lists of seven numbers a sheet, and for each one the student subtracts the smallest value from the largest. The range is the one measure on these pages that is not an average - it describes how spread out the numbers are rather than where their middle sits, which is worth saying plainly on a page that sits beside mean, median and mode.
The lists are not arranged to help. Values are drawn independently between 1 and 20, so they arrive unsorted and may repeat. Finding the range means reading the whole list twice, once for the largest and once for the smallest, and that scanning habit is what the sheet is really practising.
Subtract the smallest value from the largest. In 6, 12, 5, 16, 3, 9, 11 the largest is 16 and the smallest is 3, so the range is 13.
No. Mean, median and mode each describe where the middle of a list is; the range describes how far apart its ends are. It is taught alongside them because it is read off the same list.
They can. Values are drawn independently between 1 and 20, so a list may hold the same number twice - which does not change the range, since only the largest and the smallest matter.
Only if all seven values happened to be identical, which independent draws make vanishingly unlikely. In practice every sheet has a real subtraction on it.