Check For Understanding – Sums of Finite Geometric Series
Directions: Complete without notes and by yourself to determine whether you have mastered this
objective.
1) The formula for the sum of a finite geometric sequence is
of a1, r, and n for the sequence seen below?
. What would be the values
4, 8, 16, 32, 64, 128
2) Write the following in summation notation, starting with n = 1.
1 -3 +9 -27 + 81
3) Expand the following series and find the sum: ∑
4) Calculate the sum of the first ten terms in the following geometric series:
81, 27, 9, 3, ...
5) When Marshawn Lynch played in his first professional football season, he earned $3. For each year
after that, his salary tripled the amount that he earned from the previous year. By the time Marshawn
retired 12 years later, how much money did he earn from playing football?
Answer Key:
1) a1 = 4; r = 2; n = 6
2)
5
𝑛=
−
𝑛
3) 9 + 12 + 15 + 18 = 54
4) 121.5
5) $797,160