Question

What is the fifth term of the geometric sequence whose first three terms are 486, 162, and 54?

a. 2
b. 3
c. 4.5
d. 6
e. 9

Answer 1

6

Explanation:

an = ar^(n-1)

a = first term

n = nth term

r = common ratio

r = r2 / r1 = r3 / r2

The first 3 terms are :

486, 162, and 54

Hence,

a = 486

r = 162 / 486 = 1/3

Hence ;

a5 = 486(1/3)^5 - 1

a5 = 486(1/3)^4

a5 = 486(1 / 81)

a5 = 486 * 1 / 81

a5 = 486 / 81

a5 = 6

The 5th term of the geometric progression will be ; 6