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Life

  • 3 years ago

Write each arithmetic series as the sum of terms, find each sum.

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  1. Life
    • 3 years ago
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    |dw:1354171632278:dw|

  2. Life
    • 3 years ago
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    is the answer 20?

  3. RadEn
    • 3 years ago
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    it similar by : 3(1) + 3(2) + 3(3) + 3(4) + ... + 3(10) = 3(1+2+3+4+...+10) = ......

  4. Life
    • 3 years ago
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    so im wrong, i thought you were supposed to use the formula, Sn=n(a1+an)/2

  5. geoffb
    • 3 years ago
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    That wording is a bit interesting. Are there multiple questions like this to find the answer for, or just this one?

  6. Life
    • 3 years ago
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    yea there are about 8 questions that are under that two part question

  7. geoffb
    • 3 years ago
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    Your formula would work; you must have done it wrong.

  8. geoffb
    • 3 years ago
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    \[S_{n} = \frac{n}{2} (a_{1} + a_{n})\] Did you use 10 for \(n\) and 3 for \(a_{1}\)?

  9. RadEn
    • 3 years ago
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    for : n=1 ----> 3(1) = 3 n=2 ----> 3(2) = 6 n=3 ----> 3(3) = 9 .... so on, the series be 3+6+9+....+30 yes, use the formula like @geoffb said :)

  10. Life
    • 3 years ago
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    for n, i put 10, a1, i put 1, and for A n, i put 3

  11. geoffb
    • 3 years ago
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    Okay, that's the problem. \(a_{1}\) means the value of your first term (which is 3 times 1, or 3). \(a_{n}\) means the value of your n-th term. In this case, n is 10, so the value of the 10th term is 3 times 10, or 30.

  12. Life
    • 3 years ago
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    i got 75, am i right?

  13. geoffb
    • 3 years ago
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    No. What is your calculation?

  14. Life
    • 3 years ago
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    |dw:1354172733466:dw|

  15. geoffb
    • 3 years ago
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    Why are you using 10 for \(a_{n}\)?

  16. geoffb
    • 3 years ago
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    It wants \(a_{n}\), not \(n\).

  17. Life
    • 3 years ago
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    |dw:1354173323720:dw|

  18. geoffb
    • 3 years ago
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    That looks great.

  19. Life
    • 3 years ago
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    ughhh finally!

  20. Life
    • 3 years ago
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    so i get 330/2=165

  21. geoffb
    • 3 years ago
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    Yup. :)

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