Six - assuming 0123 does not count ... 1234 2345 3456 4567 5678 6789
-5674
There are 16 4-digit numbers that can be made up from 9 and 6.
The first digit can have 5 possible numbers, the second digit can have 4, the third 3, the fourth 2. 5
4,000 even numbers, 4,000 odd numbers.
-5674
24
Six - assuming 0123 does not count ... 1234 2345 3456 4567 5678 6789
5678 \
17
3 digit numbers are lessthan 4 digit numbers
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.
-2
12 numbers
There are 90 such numbers.
There are 9000 4-digit numbers in hindu-arabic numeration system