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To estimate \(206.345 + 331.25\) by rounding to the nearest hundreds place, we look at the numbers:

1. **Round 206.345**: The nearest hundreds place is 200 (since 206 is closer to 200 than to 300).
2. **Round 331.25**: The nearest hundreds place is 300 (since 331 is closer to 300 than to 400).

Now we can rewrite the problem with our estimates:

**Estimated Problem**:
\(200 + 300\)

**Estimated Answer**:
\(200 + 300 = 500\)

So, the estimated sum of \(206.345 + 331.25\) is **500**.