How many 3-letter sequences can be formed if the second letter must be a vowel (A, E, I, O, or U), and the third letter must be different from the first letter?
Question:
How many 3-letter sequences can be formed if the second letter must be a vowel (A, E, I, O, or U), and the third letter must be different from the first letter?
Answer:
Let's think step by step.

user
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How many 3-letter sequences can be formed if the second letter must be a vowel (A, E, I, O, or U), and the third letter must be different from the first letter?
train