**Numbers**

Four-digit Numbers

- The numbers having 4-digits are called the 4-digit numbers, provided its starting digit is not 0. For example:
3426, 3570, 1023, 02130213 is not a 4-digit number because it starts with 0.
- Four-digit numbers begin with
**1000**, read as**‘one thousand’**. - The
**smallest**4-digit number is**1000 (one thousand)**. - The
**greatest**4-digit number is**9999 (nine thousand nine hundred ninety-nine)**. - There are 9000 four-digit numbers in all.
- The greatest 3-digit number is 999. When we add 1 to 999, we get the smallest four-digit number.
- The numbers having 5-digits are called the 5-digit numbers, provided its starting digit is not 0. For example:
31426, 30570, 10023, 0321303213 is not a 5-digit number because it starts with 0.
- Five-digit numbers begin with
**10000**, read as**‘ten thousand’**. - The
**smallest**5-digit number is**10000 (ten thousand)**. - The
**greatest**5-digit number is**99999 (ninety-nine thousand nine hundred ninety-nine)**. - There are 90000 five-digit numbers in all.
- The greatest 4-digit number is 9999. When we add 1 to 9999, we get the smallest five-digit number.
- To form the greatest possible number, arrange the digits in the descending order.
- To form the smallest possible number, arrange the digits in the ascending order. If the given digits have 0, then start with the second smallest digit and use 0 in the second place.
- To form the greatest possible number, arrange the digits in the descending order and repeat the largest digits as many times as required.
- To form the smallest number, arrange the digits in the ascending order and repeat the smallest digits as many times as required. If the given digits have 0, then start with the second smallest digit and use 0 in the second place.
- One hundred is 10 times 10
- One thousand is 10 times 100
- Ten thousand is 10 times 1000

**Predecessor:**

Predecessor of a number is the number that precedes or comes before the number. To find the predecessor of a number subtract 1 from it.

**Successor:**

Successor of a number is the number that succeeds or comes after the number. To find the successor of a number, add 1 to it.

Five-digit Numbers

Forming Numbers

If some digits are given, we can form the greatest and smallest possible numbers by rearranging the given digits.

**Without repeating the digits:**

**Example:**

Form the smallest and the greatest possible 4-digits numbers using the digits 5, 7, 2, and 0.

**Answer**

**Step 1: **First arrange the digits in the ascending order to get the smallest number.

0, 2, 5, 7

Since there is a 0, start with the second smallest number, that is 2, and place the 0 at the second place.

Therefore, the smallest possible number is 2057.

**Step 2: **Arrange the digits in the descending order to get the largest possible number.

7, 5, 2, 0

Therefore, the largest possible number is 7520.

**With repeating the digits:**

**Example:**

Frame the smallest and the greatest possible 4-digits numbers using the digits 3, 6, 0.

**Answer**

**Step 1: **To get the 4-digit number, one digit has to be repeated.
Arrange the digits in the ascending order.

0, 3, 6

The smallest digit is 0. Therefore, 0 will be repeated.

The smallest possible number is 3006.

**Step 2: **Arrange the digits in the descending order.

6, 3, 0

The largest digit is 6. Therefore, 6 will be repeated.

The greatest possible number is 6630.

**Fun facts:**

**Did you know?**

ATM cards have a unique **Personal Identification Number (PIN).** Generally, a PIN is a **4-digit** code.
You can make 10000 different 4-digit codes using the digits 0 to 9.