Johnny has a locker combination with 1 letter followed by three digits. none of the digits can repeat themselves. how many combinations are there in the sample space? (theoretical probability and simulations) me find the answer.

 First, what letter can it be at the beginning?

English Alphabet has 26 letters, so we have 26 possibilities

26*

then it can be any of 10 digits

26*10=260

then any of the remaining 9 digits:

26*10*9

then any of the remaining 8 and 7 digits:

26*10*9*8*7=131040

so the solution is: 131040 possible combinations!

The first one, i believe, would be correct. all the others have one thing in common, and that's that they have repeating numbers. in the second one, x and y have repeating 6's and 3's, and in the third, x and y have repeating 6's as well. in the last one, there are repeating 3's. the first one has no repeating numbers.