What is the sum of the geometric sequence 1, 3, 9, ... if there are 11 terms?
Solution:
The formula to find the sum of geometric sequence is
a(rn - 1)/ (r - 1)
Where a is the first number
r is the common ratio
n is the number of terms
It is given that
a = 1
r = 3/1 = 3
n = 11
Substituting it in the formula
Sum of the geometric sequence = a(rn - 1)/ (r - 1)
= 1 (311 - 1)/ (3 - 1)
By further calculation
= 1 (177147 - 1)/ 2
= 177146/ 2
So we get
= 88573
Therefore, the sum of the geometric sequence is 88573.
What is the sum of the geometric sequence 1, 3, 9, ... if there are 11 terms?
Summary:
The sum of the geometric sequence 1, 3, 9, ... if there are 11 terms is 88573.
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