Hi dpo28,
Based on the description in the first example, you can use EITHER 3 numbers (1,3,5,7,9) with NO repeats OR you can use 3 vowels (A,E,I,O,U) with NO repeats.
With a license plate, there is an ORDER to the characters (and the order DOES matter), so we have a permutation.
With just numbers, and 3 "spots" we would have....
5 options for the first 'spot'; once we place a number, we then have....
4 options for the second 'spot'; once we place a number, we then have...
3 options for the third 'spot;
(5)(4)(3) = 60 different licenses with numbers
With just vowels, we have the exact same mathematical situation: 5 vowels and 3 "spots":
5 options for the first 'spot'; once we place a vowel, we then have....
4 options for the second 'spot'; once we place a vowel, we then have...
3 options for the third 'spot;
(5)(4)(3) = 60 different licenses with vowels
60+60 = 120 total licenses under these restrictions.
GMAT assassins aren't born, they're made,
Rich
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