SOLUTION: What is the sum of a 30–term arithmetic sequence where the first term is 73 and the last term is –101?
Algebra.Com
Question 639176: What is the sum of a 30–term arithmetic sequence where the first term is 73 and the last term is –101?
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
The formula is Sn = (n*(a1 + an))/2
In this case,
a1 = 73
an = -101
n = 30
Plug all this into the formula above to get
Sn = (n*(a1 + an))/2
Sn = (30*(73 + -101))/2
Sn = (30*(-28))/2
Sn = (-840)/2
Sn = -420
So the answer is -420
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