# Find the sum of the terms of arithmetic -5, -3, -1,1......55

Find the sum of the terms of arithmetic -5, -3, -1,1......55
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Mohammed Farley
55=−5+(n−1)2
55=−5+2n−2
55=−7+2n
62=2n
31=n
Now, we can use the formula ${s}_{n}=\frac{n}{2}\left(2a+\left(n-1\right)d\right)$
${s}_{31}=\frac{31}{2}\left(2\left(-5\right)+\left(31-1\right)2\right)$
${s}_{31}=\frac{31}{2}\left(50\right)$
${s}_{31}=31×25$
${s}_{31}=775$
The sum of the terms is 775.