To arrange the numbers $-1$, $-3.15$, and $-\frac{1}{9}$ from least to greatest:

1. $-3.15$
2. $-1$
3. $-\frac{1}{9}$ (which is approximately $-0.11$)

So the order is:

$-3.15 < -1 < -\frac{1}{9}$

Would you like further explanation or any details on this? Here are 5 related questions for practice:

1. How would you order $-2$, $-0.5$, and $-\frac{4}{3}$?
2. What is the decimal value of $-\frac{1}{5}$?
3. How do you convert fractions like $-\frac{1}{9}$ into decimals?
4. How do negative numbers behave on a number line?
5. What is the smallest negative number: $-100$, $-10.5$, or $-0.01$?

Tip: Negative numbers further from zero are always smaller than those closer to zero.