Let's first evaluate the numbers given:

1. $\frac{1}{3}$ ≈ 0.33
2. 1.8 (given directly)
3. $\pi$ ≈ 3.14
4. $\sqrt{6}$ ≈ 2.45
5. $\sqrt{25} = 5$
6. 6 (given directly)

Now we order these from least to greatest: $\frac{1}{3} \approx 0.33, \ 1.8, \ \sqrt{6} \approx 2.45, \ \pi \approx 3.14, \ \sqrt{25} = 5, \ 6$

The correct order is: $\frac{1}{3}, \ 1.8, \ \sqrt{6}, \ \pi, \ \sqrt{25}, \ 6$

Now, let's check which option graphs these numbers correctly in increasing order:

• Option C is the correct answer.

Would you like any further details on the solution?

Here are 5 related questions you might want to explore:

1. How is $\pi$ defined, and why is it irrational?
2. How do you compute square roots of non-perfect squares?
3. What are rational and irrational numbers?
4. How do you estimate square roots without a calculator?
5. Can all numbers be represented on a number line?

Tip: When comparing irrational numbers like $\pi$, it helps to use an approximate decimal value for clarity.