This is a statistics problem on permutation and combination. To differentiate this, permutation involves on the arrangement in which order doesn't matter. For combination, order matters.
For example, if you arrange A, B and C, for permutation it could be AB, BA, CA, AC, BC and CB. But for combination, it would just be AB, AC and BC.
So, in this problem where he is asked to arrange 8 jars in which order doesn't matter. It is permutation. You can solve this just by calculator. The formula would be nPr, where n is the total number of items while r is the number of items to be sorted. Thus,
8 square inches. You find area by length x height. A square's sides are all of equal length. So what number x itself is 64? The answer is 8 because 8 x 8 equals 64.
From the question, we want to find the probability of selecting a slip of paper with the letter t on it, then selecting the letter r, with replacement.
This means the probability of selecting t and r.
That is
There are 12 letters (total outcomes). And there are 2r and 2t.