Write the successor and predecessor of
(i) 1000.
(ii) 1005399.
(iii) 999999.

Answer

To find the successor and predecessor of the given numbers, we will follow these steps:

### Step-by-Step Solution:

1. **Understanding Successor and Predecessor:**
- The **successor** of a number is the number that comes immediately after it. It is found by adding 1 to the number.
- The **predecessor** of a number is the number that comes immediately before it. It is found by subtracting 1 from the number.

2. **Finding Successor and Predecessor for 1000:**
- **Successor of 1000:**
\[ 1000 + 1 = 1001 \]
- **Predecessor of 1000:**
\[ 1000 - 1 = 999 \]

3. **Finding Successor and Predecessor for 1005399:**
- **Successor of 1005399:**
\[ 1005399 + 1 = 1005400 \]
- **Predecessor of 1005399:**
\[ 1005399 - 1 = 1005398 \]

4. **Finding Successor and Predecessor for 999999:**
- **Successor of 999999:**
\[ 999999 + 1 = 1000000 \]
- **Predecessor of 999999:**
\[ 999999 - 1 = 999998 \]

### Final Answers:
- For 1000:
- Successor: **1001**
- Predecessor: **999**

- For 1005399:
- Successor: **1005400**
- Predecessor: **1005398**

- For 999999:
- Successor: **1000000**
- Predecessor: **999998**