Answer:
Step-by-step explanation:
Lets look at the first pick. There are 9 items that can be choosen, one that cannot. So the chance to not pick the one is 9/10.
All the other attempts are the same and have 9/10 chance. (as replacement happens)
Now these events are independent of eachother so the combined chance is
(9/10)^10
For the formula:
Number of items: n
One pick is: (n-1)/n
N pick together is [(n-1)/n]^n