+1678 How many ways can you write two different letters chosen from
A B C D E F G H I J K L M N O P
so that they are in alphabetical order, and the first letter is a vowel? For example, AF and EN count, but DE and KC do not.
+1277
How many ways can you write two different letters chosen from
A B C D E F G H I J K L M N O P
so that they are in alphabetical order, and the first letter is a vowel?
two different letters
in alphabetical order
the first letter is a vowel
If the first letter is A, then there are 15 possibilities. (Second letter can be anything past A.)
If the first letter is E, then there are 11 possibilities. (Second letter can be anything past E.)
If the first letter is I, then there are 7 possibilities. (Second letter can be anything past I.)
If the first letter is O, then there is 1 possibility. (Second letter can be only P.)
Add them up. 34 possibilities.
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