1. The problem asks: Which is greater, $-3.1$ or $-3.01$? 2. To compare two negative decimals, remember that the number closer to zero is greater because negative numbers decrease in value as they move away from zero. 3. Here, $-3.1$ is the same as $-3.10$ for comparison purposes. 4. Comparing $-3.10$ and $-3.01$, since $-3.01$ is closer to zero, it is greater than $-3.10$. 5. Therefore, $-3.01 > -3.1$. Final answer: $-3.01$ is greater than $-3.1$.