In both instances, there is a 20% chance that he gets a striped sweater. 2 x 2/10 is not the same as 2/10 x 2/10. You have to do 2/10 x 2/10, because there's a 20% chance he gets it first, and then 20% he gets it again. The chance he gets it twice in a row should be 4 out of 100 or 1 out of 25. A very slim chance
The probability to select a stripped shirt is 2/10 He replaced it, then the number of shirts is the same & the probability is the same. But here there is a conditional probability 1st selection P(2/10) AND 2nd selection P(2/10) so P( stripped shirt AND another stripped shirt) =2/10 x2/10= 4/100 =1/25
