Question

What is the value of the fourth term in geometric sequence for which a1 = 15 and r = 1/3?

Answer 1

So you express fraction. 
15 x (1/3)^ 3=15/27=5/9

Answer 2

Answer:

the fourth term is 5/9

Step-by-step explanation:

a sequence is defined like this:

1, 2, 3,4…….. n  

1= first term

2=second term

3= third term

n=term n of the secuence

a geometric sequence is defined as follows

$a,ar,ar^{2} ,ar^{3} ,..............ar^{n-1}$

The General formula to calculate the term n of a geometric sequence is:

                 $term(n)=ar^{n-1}$        Formula (1)

We can calculate any term of the sequence by replacing the information known in the formula (1):

For this case: a=a1=15 ,   r=1/3

               $term(n)=15*(1/3)^{n-1}$   Formula (2)

We replace n=4 in the formula 2  

            $term(4)=15*(1/3)^{4-1}$

$term(4)=15*(1/3)^{3}$

$term(4)=15*(1/27)$

$term(4)=5/9$

The fourth term of the geometric sequence is 5/9