I. Determine the dates
Ask someone to select three consecutive days or three dates with the same day on three consecutive weeks. They are to give you the total number from the sum of the dates.
You determine the correct dates by dividing their answer by 3. You then must ask if the dates are in the same week.
If they are in the same week, add and subtract one from your derived number to tell the dates.
If they are not in the same week, add and subtract 7 from your number to give the dates.
In the above calendar, adding 11, 12, and 13 would produce a total of 36 which divided by 3 = 12. In the same week, this would result in the dates of 11, 12, and 13. If not in the same week, then the results are 5, 12, and 19.