Assuming you don't include numbers like 0673, then there are 9000 - all the numbers from 1000 to 9999. (It's not 8999 as one might expect, because the calculation requires the inclusivedifference.)
It is 1,000.
1000
There are 504 such numbers.
100,000
6
4digit number
5295
It is 1,000.
100000000000 kantutan
9000
1000
There are 504 such numbers.
100,000
9999
The question to help my son with his homework is: How many unique numbers can be formed by combining three sets of three digital decimal numbers
There are 60480 numbers.
840