1) The document discusses methods for determining the middle number, or average, of a set of consecutive numbers given their sum. It provides examples of calculating the middle number from the sum of 3, 5, and other numbers of consecutive terms.
2) Rules are given for calculating the middle number from the sum of consecutive integers, consecutive even numbers, and consecutive odd numbers. The method is to divide the total sum by the number of terms.
3) Once the middle number is determined, the document describes how to calculate the other terms by subtracting and adding 1 from the middle number for consecutive integers, and adding/subtracting 2 for consecutive even/odd numbers.