You have 6 options for the first digit, 5 for the next, 4 for the next, and 3 for the next. Multiply all those numbers together.
There are twelve possible solutions using the rule you stated.
24680
9
-8
That's simple enough. Just count the numbers from 0 to 999,999 and you will find there are one million of them.
There are 840 4-digit combinations without repeating any digit in the combinations.
Number of 7 digit combinations out of the 10 one-digit numbers = 120.
There are twelve possible solutions using the rule you stated.
24680
120 combinations using each digit once per combination. There are 625 combinations if you can repeat the digits.
There are only six combinations using you rule. They are:- 235, 237, 325, 327, 723 and 725
Not repeating, it is 7*6*5*4 which is 840 ways ---- There are 7 choices for each of four digits, right? 74 = 2401
There are 15C3 = 15*14*13/(3*2*1) = 455 combinations, and I am NOT even going to try listing them.
9
-8
That's simple enough. Just count the numbers from 0 to 999,999 and you will find there are one million of them.
It depends. If you can only use each number once, there are 720 combinations. If you can use numbers multiple times, then there are 1000 combinations, by using all numbers from 000 to 999.