How many strings of eight letters are there if no letters can be repeated?

To find the number of strings of eight letters with no repetitions, we can use permutations. If we assume we have 26 letters in the English alphabet, the first letter can be any of the 26, the second letter can be any of the remaining 25, the third can be any of the remaining 24, and so on. Therefore, the total number of strings is calculated as (26 \times 25 \times 24 \times 23 \times 22 \times 21 \times 20 \times 19), which equals 3,315,312,000.