What is the possibility of choosing four different numbers out of 28

"When choosing one number randomly out of 28 different numbers, what is the probability that this may be done four times, from the same set of 28 numbers, and no number will be drawn twice?"

Well if there are 28 different numbers in a hat and you randomly chose 4 of them without replacement.  Then there is 100 % certainty that they will all be different.  

The probability is 1

28/28 x 27/28 x 26/28 x 25/28 = 0.7994715743440233

79.9%

Yes anon that is one one interpretation.   But you should state exactly what question you have answered.

Thank you :))