The sixth term is exactly halfway between the fourth and the eighth in the arithmetic sequence, so it is the average of the two terms. Therefore, the sixth term is $(200 + 500)/2 = \boxed{350}$.  We also could have found the common difference by noting that there are four steps between the fourth term and the eighth term.  So, if $d$ is the common difference, we have $4d = 500-200 = 300$. Therefore, we find $d=75$.  The sixth term is two steps after the fourth, or $200 + 2d = \boxed{350}$.
Question:
If the fourth term of an arithmetic sequence is $200$ and the eighth term is $500$, what is the sixth term?
Answer:
Let's think step by step.

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350
If the fourth term of an arithmetic sequence is $200$ and the eighth term is $500$, what is the sixth term?
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