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prealgebra intermediate

Problem

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?
Solution
There are 26 options for the first letter, only 5 options for the second (vowels only), and 25 options for the third letter (all letters but the first letter). This gives combinations.
Final answer
3,\!250