This document discusses arithmetic progressions (AP). It defines an AP as a sequence of numbers where the difference between any two consecutive terms is constant. Examples of APs include the sequences 1,2,3,4... and 3,5,7,9,... which have common differences of 1 and 2 respectively. Formulas are provided for calculating the nth term, sum of the first n terms, and other properties of APs. Questions and solutions about finding terms and common differences of APs are also presented.