Since they are different people with different thoughts and knowledge giving them to choose different numbers all though two of them might choose the same number
If one person chooses a number from 1-5 already, they basically have any choice between 1-5 at their disposal. Therefore, there is not much of a probability for them. If the next individual's number will be different, there will be 4 numbers left. Additionally, this means that the next person (let's say Ben) will have a probability 4/5 since that is if he chooses a different number. There will be 3 numbers remaining, so the last person who picks will have a probability of 3/5.
3/5 and 4/5 are boh probabilities, so multiply them together to get one, which is 12/25.
