A permutation problem based on code word
- Thread starter sanjeev
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What do you mean by "two distinct English alphabets"? Do you perhaps mean "alphabetic characters", so you're needing two different letters?
Okay, okay; there's no need to SHOUT. :-(
Have you done any exercises of this sort before, or are you needing lesson instruction first? Thank you!
HallsofIvy
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The first can be any letter. How many choices are there? The second can be any letter except whatever you used for the first. How many choices are there? The third can be any digit from 1 to 9. How many choices are there? The fourth can be any digit except whatever you used for the third. How many choices are there?
"Fundamental law of counting"- if you can do one thing in m different ways and a second in n different ways, you can do both of them in mn different ways.
"Fundamental law of counting"- if you can do one thing in m different ways and a second in n different ways, you can do both of them in mn different ways.
If the book's answer for the number of permutations is correct, then I think we need to interpret the word "between" literally -- that is, the digits in-between 1 and 9.
In this case, the given phrase "2 distinct numbers between 1 and 9" would be better phrased as "two distinct digits from 2 through 8".
Cheers