12 numbers
2240
-4
2
If you want 4-digit numbers, there are 24 of them.
There are 2941 4-digit numbers such no two of its digits differ by 1.
There are 16 4-digit numbers that can be made up from 9 and 6.
12 numbers
9999
2240
10,000
-4
To find the number of 4-digit numbers that are multiples of 9, we first determine the range of 4-digit numbers, which is from 1000 to 9999. Next, we calculate the first and last multiples of 9 within this range, which are 1008 and 9999 respectively. To find the total number of multiples of 9 in this range, we divide the difference between the last and first multiples by 9 and add 1, resulting in (9999 - 1008) / 9 + 1 = 999. Therefore, there are 999 4-digit numbers that are multiples of 9.
There are 10 possible digits (0-9) for each of the four positions in a 4-digit number. Therefore, the total number of 4-digit numbers is calculated by multiplying the number of choices for each position: 10 choices for the thousands place, 10 choices for the hundreds place, 10 choices for the tens place, and 10 choices for the units place. This results in a total of 10 x 10 x 10 x 10 = 10,000 possible 4-digit numbers from 0000 to 9999.
2
The first digit can have 5 possible numbers, the second digit can have 4, the third 3, the fourth 2. 5
If you want 4-digit numbers, there are 24 of them.