Question

Of the five letters (A,B,C,D,E), two unique letters are to be selected at random. How many possible selections?

Please explain.

Answer 1

Something like that

Answer 2

For slot 1, you have 5 choices

After you pick a letter, you have 4 choices for slot 2.

If order mattered, then you would just multiply 5*4 = 20

But order doesn't matter in this case (AB is the same as BA), so you divide by 2 to correct for double counting

20/2 = 10

so that's why the answer is 10

Answer 3

= 5x4/2x1 = 10
there are 10 possible selections

Answer 4

iYuko that first method is flawed unfortunately. If you tried it with say six letters, you would get

6*2 = 12

but if you had 6 letters, the actual answer is (6*5)/2 = 30/2 = 15

Answer 5

Thank you! it makes sense now

Answer 6

yw