. Sum to n terms of a Geometric progression A series whose terms are in Geometric progression is called Geometric series. Let a , ar , ar , ... ar n - , ...
be the Geometric Progression. The sum of first n terms of the Geometric progression is S ar ar ar ar ... ( ) Multiplying both sides by r , we get rS ar ar ar ar ar … ( ) ( ) − ( ) ⇒ rS S ar S r a r Thus, the sum to n terms is S a r ), r ¹ .