SOLUTION: Trying to find the sum 41+42+43+44+.....+118

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Question 619384: Trying to find the sum 41+42+43+44+.....+118
Found 2 solutions by ewatrrr, nerdybill:
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi,

finding the sum  of sequence: 41+42+43+44+.....+118

Arithmetic Sequence with a%5B1%5D+=+41 and d = 1

a%5Bn%5D=a%5B1%5D%2B%28n-1%29%2Ad

a%5Bn%5D=+41%2B%28n-1%29%2A1+=+118

     n = 118-41 + 1

     n = 78

S%5Bn%5D=%28n%2F2%29%282%2Aa%5B1%5D%2B+%28n-1%29d%29

S%5B78%5D=%2878%2F2%29%282%2A41%2B+%2877%291%29

S%5B78%5D=%2839%29%28159%29

S%5B78%5D=+6201

Answer by nerdybill(7384) About Me  (Show Source):
You can put this solution on YOUR website!
Trying to find the sum 41+42+43+44+.....+118
.
Partial sum of an arithmetic sequence:
S = n((a1+an)/2)
where
S = sum of n numbers
n = 118-40 = 78
a1 = 41
an = 118
.
S = 78((41+118)/2)
S = 78(159/2)
S = 78(79.5)
s = 6201