What is the units digit of $3^1 + 3^3 + 3^5 + 3^7 + \ldots + 3^{2009}$?
Question:
What is the units digit of $3^1 + 3^3 + 3^5 + 3^7 + \ldots + 3^{2009}$?
Answer:
Let's think step by step.

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What is the units digit of $3^1 + 3^3 + 3^5 + 3^7 + \ldots + 3^{2009}$?
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