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This is a permutation problem where we can use P(n,r)= n!/(n−r)!

You are arranging 3 pairs of students, where order matters (which pair performs first, second, third). When order matters, we use permutations. First lets arrange the 3 pairs of students by plugging into the permutation formula.

Step 1.
P(3,3)= 3!/(3!-3!)!
=3!/0! (zero becomes 1)
=3!/1
=3*2=6

Step 2.
Now, for each pair of students (say, A and B), there are only 2 students to arrange. The only possible arrangements are:
A goes first, B goes second
B goes first, A goes second
there are only 2 possible orders which is 2! or 2
we do this three times which = 2*2*2= 2^3=8

Multiply both results = 6*8=48




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Lovely ordering problem: 3! orders for P, Q, R, and 2 orders within each of the pairs, so 3! *2*2*2:
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Initially I had used the usual method 3x2x1 to select pair order and then x8 for intro order to get 48 , but later opted for 12 based on below workings. Can somebody let me know why below approach is wrong ,
aren't we supposed to select sequentially without replacement , after choosing 1st pair , 2 pairs are left and then 1 pair.

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Hello, what would it mean to do 6!/(2!*2!*2!) in this example? How does it differ from doing 3!*2!*2!
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