The question asks to arrange the following numbers in descending order: 3, 8, 2.1, -0.12, √5.

To begin with:

1. The number 8 is the largest.
2. √5 (approximately 2.236) comes next.
3. 3 is slightly smaller than √5.
4. 2.1 follows.
5. -0.12 is the smallest value, as it's negative.

So, the numbers in descending order are:

8, √5, 3, 2.1, -0.12

Would you like more explanation on any of these steps or have any other questions?

Here are some additional related questions:

1. How do we estimate the square root of numbers like √5 without a calculator?
2. What is the significance of negative numbers in ordering?
3. Can we use approximation for irrational numbers like √5 when comparing them?
4. How does ordering help in real-world scenarios like budgeting or ranking?
5. What are the differences between descending and ascending order?

Tip: When comparing square roots or irrational numbers, try using approximations to make the comparison easier.