Please explain Find the sum of the infinite geometric series

Please explain.

Find the sum of the infinite geometric series. (If an answer is undefined, enter UNDEFINED.) 36 + 30 + 25 + 125/6 +...

Solution

infinite gp are a, ar,ar^2 ,a^3,.................................a^n-1

so here r =common ratio

36 +30 +25 +125/6 +............

a =36 ar =30

36r=30

r = 30/36 =5/6

the sum of infinite Gp is = a/1-r

= 36/(1-5/6)

= 36/(1/6)

=36*6

=216