[latexpage]
A progression of numbers in which every term bears a constant ratio with its proceeding term is called a Geometrical Progression(G.P.)
The constant ratio is called common ratio.
$a, ar, ar^2, ar^3……ar^n$
$Tm = ar^{m-1}$
$Sm= a \frac{(1-r^n)}{(1-r)}$