To determine which number is larger, you can compare the digits in each place value, starting from the left.

1.  **Compare the ones place:** Both numbers have a **9** in the ones place, so they are equal so far.
2.  **Compare the tenths place (the first digit after the decimal):**
    *   9.11 has a **1** in the tenths place.
    *   9.9 has a **9** in the tenths place.

Since 9 is larger than 1, **9.9 is the larger number.**

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*Another way to think about it:*
You can add a zero to the end of 9.9 to make it 9.90 without changing its value. Now you are comparing:
*   9.11
*   9.90

It's easier to see that 90 is larger than 11, which means **9.90 (or 9.9) is larger than 9.11.**
