[Maths]Probability

Q1 : P(they both get less than 60 marks in the quiz)= P(the 1st is less than 60 marks) x P(the 2nd is less than 60 marks)= 34/40 x 33/39= 187/260
(This answer is including AB and BA as their marks are less than 60.)
Q2 : P(only one of them passes the quiz)= P(the 1st gets 55 or above) x P(the 2nd gets below 55) + P(the 1st gets below 55) x P(the 2nd gets 55 or above)= 16/40 x 24/39 + 24/40 x 16/39= 32/65
(AB is different from BA, as A >= 55 and B < 55.)

The question also asks for another thing: Find the probability that only one of them passes the quiz given that the passing mark for the test is 55.

Ans:(16/40 x 24/39) + (24/40 x 16/39) = 32/65

Why do I have to consider about the order of student A and B in this situation?

'selected' 暗示咗係combination，所以唔洗理會次序。
例如AB=BA