Write in order from least to the greatest `:` 2.1,2.105,2.011.

Answer

To arrange the numbers 2.1, 2.105, and 2.011 from least to greatest, we can follow these steps:

### Step 1: Convert to Like Decimals
We need to convert all the numbers to have the same number of decimal places. The highest number of decimal places among the given numbers is three (as seen in 2.105 and 2.011). Therefore, we will convert 2.1 to have three decimal places.

**Conversion:**
- 2.1 becomes 2.100 (adding two zeros).

Now we have:
- 2.100
- 2.105
- 2.011

### Step 2: Compare the Numbers
Now that all numbers have the same number of decimal places, we can compare them directly.

- 2.100
- 2.105
- 2.011

### Step 3: Arrange in Order
We will compare the numbers starting from the leftmost digit after the decimal point:

1. Compare the first decimal place:
- 2.100 (1)
- 2.105 (1)
- 2.011 (0)

Since 0 is the smallest, 2.011 is the least.

2. Next, we compare 2.100 and 2.105:
- 2.100 (0)
- 2.105 (0)

Since 0 is the same, we move to the next decimal place:
- 2.100 (0)
- 2.105 (5)

Since 5 is greater than 0, 2.105 is greater than 2.100.

### Final Order
Putting it all together, we have:
- Least: 2.011
- Middle: 2.100
- Greatest: 2.105

Thus, the order from least to greatest is:
**2.011, 2.100, 2.105**