In a four digit code numbers 0-9, what are all the possible different combinations of numbers. Assume the numbers can be used twice

There are 10 digits from 0 to 9. If repetition is allowed, then we have

10*10*10*10=10,000 possibilities. Think about it. How many 4 digit numbers are there from 0000 to 9999? There are 10,000.

Now, if repetition is NOT allowed, then we have 10 choices for the first, 9 for the second, 8 for the third, 7 for the fourth.

10*9*8*7=7!=5040.

Now, with these as an idea, how many are there with a number used twice?

HEY GALACTUS, is there anywhere I can get all of those different combinations? AND YES, any number can be used more than once.

All 10,000? Think about it. Those 10,000 combinations would be all the numbers from 0000 to 9,999. Just count to 10000