# How do you find #a_9# when #a_1 = 1000, r = 1/3?#

##### 1 Answer

May 25, 2016

#### Explanation:

For the standard geometric sequence.

#a,ar,ar^2,ar^3,..............,ar^(n-1)#

where a is 1st term

r ,the common ratio

#=a_2/a_1=a_3/a_2=....=a_n/a_(n-1)# and the nth term

#a_n=ar^(n-1)# here n = 9 , a = 1000 and

#r=1/3#

#rArra_9=1000(1/3)^8=1000/3^8=1000/6561#