Answer
$40.5$
Work Step by Step
Infinite geometric sequence with first four terms 27, 9, 3, 1
$9/27 = 1/3$
$3/9 = 1/3$
$a_1 = 27$
$r = 1/3$
$S = a_1/(1-r)$
$S = 27/(1-1/3)$
$S = 27/(2/3)$
$S = 27*3/1*3 /(2/3)$
$S = 81/3 /(2/3)$
$S = 81/2$
$S = 40.5$
