Question

Four letters are chosen at random from the letters A, B, I, K, N, O, and T. What is the size of the sample space of this experiment? Assume that the order of the letters matters. That is, ABIK is different from BAIK.

Answer 1

The sample size is 7P4
That's permutations of 7 things taken 4 at a time
and it equals 7x6x5x4 or 840
Another way to think of it
There are 7 choices for the first letter
For each of these 7 possibilities there are 6 choices for the 2nd letter
Then 5 choices for the third letter
Then 4 choices for the fourth