Answer:
77.4
Step-by-step explanation:
The first term, a, of the series is 3.
It is a geometric progression, so we can calculate the common ratio, r:
3.75 / 3 = 1.25
The sum of n terms of a geometric progression is given as:
[tex]S = \frac{a(1 - r^n)}{(1 - r)}[/tex]
where n = number of terms considered
The sum of the first 9 terms will therefore be:
[tex]S_9 = \frac{3(1 - 1.25^9)}{(1 - 1.25)} \\\\S_9 = \frac{3(1 - 7.45)}{-0.25}\\ \\S_9 = \frac{3 * -6.45}{-0.25}\\ S_9 = \frac{-19.35}{-0.25}\\ \\S_9 = 77.4[/tex]
