Question

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

Express your answer as a fraction.

Answer 1

$a_1=15;\ r=\dfrac{1}{3}\\\\a_n=a_1r^{n-1}\to a_n=15\cdot\left(\dfrac{1}{3}\right)^{n-1}\\\\a_4=15\cdot\left(\dfrac{1}{3}\right)^{4-1}=15\cdot\left(\dfrac{1}{3}\right)^3=15\cdot\dfrac{1}{27}=\dfrac{15}{27}=\dfrac{5}{9}\\\\\\Answer:\boxed{a_4=\frac{5}{9}}$

Answer 2

Answer:5/9

Step-by-step explanation:

Apex