SOLUTION: In an arithmetic series, the terms of the series are equally spread out. For example, in 1 + 5 + 9 + 13 + 17, consecutive terms are 4 apart. If the first term in an arithmetic ser

Algebra ->  Sequences-and-series -> SOLUTION: In an arithmetic series, the terms of the series are equally spread out. For example, in 1 + 5 + 9 + 13 + 17, consecutive terms are 4 apart. If the first term in an arithmetic ser      Log On


   

Question 849725: In an arithmetic series, the terms of the series are equally spread out. For example, in
1 + 5 + 9 + 13 + 17, consecutive terms are 4 apart. If the first term in an arithmetic series is
3, the last term is 136, and the sum is 1,390, what are the first 3 terms?
Answer by swincher4391(1107) About Me  (Show Source):
You can put this solution on YOUR website!
Sn = (A1 + An)/2 * n
1390 = (3+136)/2 * n
2780 = 139n
n = 20
136 = 3 + (20-1)*d
136 = 3 + 19d
133 = 19d
d = 7
3, 3+7, 3+2*7
3,10,17