Problem: Let s be the limiting sum of the geometric series 4−38+916−…, as the number of terms increases without bound. Then s equals:
Answer Choices:
A. a number between 0 and 1
B. 2.4
C. 2.5
D. 3.6
E. 12
Solution:
Since 1+a+a2+…=1−a1 when ∣a∣<1, the required limiting sum equals 1−(−32)4=2.4