Question

How many strings of eight English letters are there:__________ a) that contain no vowels, if letters can be repeated? b) that contain no vowels, if letters cannot be repeated? c) that start with a vowel, if letters can be repeated? d) that start with a vowel, if letters cannot be repeated?

Answer 1

Answer:

a) that contain no vowels, if letters can be repeated

Explanation:

since strings of eight English letters contain no vowels, so there are 21 choices for each of the eight letters.