SOLUTION: Find the sum of the arithmetic sequence. 251, 249, 247, 245, ..., 233

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Question 1140694: Find the sum of the arithmetic sequence.
251, 249, 247, 245, ..., 233
Answer by dkppathak(439) About Me  (Show Source):
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Find the sum of the arithmetic sequence.
251, 249, 247, 245, ..., 233
solution
a=251 d=249-251=-2 last term=233
last term=a+(n-1)d
233=251+(n-1)x-2
233-251=-2(n-1)
-18=-2(n-1)
n-1=9
n=10
sum=10(251+233)/2
=10x484/2
10x242=2420
answer 2420