Both “different” and “3-digit” are adjectives in the sentence.
The structure of two nouns joined together by a hyphen is often used to create a “dual word” adjective before the noun. It is called a compound adjective.
“The “latex-free gloves are better for my hands.”
“Yesterday, he ran the 100-yard dash.”
In the sentence, both “different” and “3-Digit” are adjectives modifying the noun “numbers”.
If we had wanted to say different digits, one way could have been:
“How many 3-digit numbers with different digits are possible.?”
As written, the sentence states that we are looking for numbers/arrangements that are both “different” (I.e., unique) and that have “3-digits.”
soondoobu
This is a poorly written question. There is no correct answer. The question states that all 3 digits are different. So, the number of different 3-digit license plate that can be formed is 9 * 9 * 8 = 648.
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