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? A. 3, 10, 17 B. 3, 23, 43 C. 3 , 36.333 , 70 D. 3, 69.5, 136 2 E. 3, 139, 1,251
first term is given..last term is given...and sum is given... so use summation formula to get the number of terms \[\huge s_n = \frac{n(a_1 + a_n)}2\] does that help?
Yes! Thank you very much.
welcome
wait, What is N??
the number of terms? would 3 be n in this case?
You can solve for n using that equation.
You'll need to find how far apart (the equal spacing) between the terms is.
Also, since it's multiple choice, you can eliminate some of those answer choices because the terms are not equally spaced.
yes. n is the number of terms. And no, 3 is the first term so it's a1
an is the last term so that would be 136 sn is the sum so that would be 1390
And n is not 3 just because they are asking for the first 3 terms either.
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