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The first and last terms of a 10-term arithmetic series are listed in the table. What is the sum of the series?


Term Number Term
1 3
10 75

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The sum of an arithmetic series:
[tex]S_n=\frac{n(a_1+a_n)}{2}[/tex]

[tex]a_1=3 \\ a_{10}=75 \\ \\ S_{10}=\frac{10(a_1+a_{10})}{2}=\frac{10(3+75)}{2}=5(3+75)=5 \times 78=390[/tex]

The sum of the series is 390.

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