A sequence is an ordered list of numbers, we mean an arrangement of numbers in definite order according to some rule. The sum of all the terms of a sequence is a series, then the sum expressed as a1 + a2 + a3 + … is called series. A series is called finite series if it has a finite number of terms. The chapter discusses the following topics which include Sequence and Series, Arithmetic Progression (A. P.) is a sequence in which terms increase or decrease regularly by the same constant. This constant is called the common difference of the A.P. Arithmetic Mean (A.M.), Geometric Progression (G.P.) , general term of a G.P., the sum of first n terms of a G.P., infinite G.P. and its sum, geometric mean (G.M.), the relation between A.M. and G.M, formulae for the special series sums and more.