SOLUTION: what are all of the possible combinations that can be made of 4 digits using numbers 0-9?

Question 370261: what are all of the possible combinations that can be made of 4 digits using numbers 0-9?
Found 2 solutions by edjones, Year 11 kid:
Answer by edjones(8007) (Show Source): You can put this solution on YOUR website!
nCr=combination of n things taken r at a time= n!/((n-r)!r!)
Arrangement is not important.
=10!/(6!*4!)
=210
.
Ed
Answer by Year 11 kid(1) (Show Source): You can put this solution on YOUR website!
The answer of the another tutor is totally wrong.
As we know, "0" cant be the first digit, so there is 9 possible choice of the first place,as the question doesnt say we cant repeatly use the number, that we have 10 choices in the second, third and the last place,
there are 9x10x10x10=9000 ways of managing the digit.
P.s I am only a year 11 kid and I am an EAL students. Plz ignore the typos or grammar mistakes.
RELATED QUESTIONS
Ed made a list of all the two-digit numbers that can be formed using two different digits (answered by richwmiller)
WHAT ARE ALL THE DIFFERENT 4 DIGIT COMBINATIONS THAT CAN BE MADE FROM THE NUMBERS 1-9... (answered by stanbon)
lock combinations are made by using 4 digits. how many different lock combinations can be (answered by Alan3354)
Locks combinations are made by using 4 digits. How many different lock combinations can... (answered by stanbon)
Lock combinations are made by using 4 digits. How many different lock combinations can be (answered by Fombitz)
Lock combinations are made by using 4 digits. How many different lock combinations can... (answered by stanbon)
All six digit numbers that can be formed using the digits 2 3 5 6 7 and 9 are written.... (answered by solver91311)
How many different license plates can be made that have one letter followed by 4... (answered by Edwin McCravy)
Serial numbers for a product are to be made using 4 letters followed by 2 numbers. If... (answered by stanbon)