Thread: Need help with Counting Rule and Permutations

How many ways can a person select four books, two CDs, and one DVD from ten books, twenty CDs, and five DVDs?

How many different three letter permutations can be formed from the letters in the word clipboard?

How many 3-digit codes using the digits 0 through 9 are possible if repetitions are allowed?


I'm gettng confused. Please help! Thanks!

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For the first one I tried calculating all of ways that each item could be counted. So I fgured you can just multiple each one 4x2x1x10x20x5 but I dont think thats right.

For the second and third one, I think that the answer is 729 if you multiply being able to perform 9 letter/number combos 3 times or 9^3 but I dont think that's right either.

Originally Posted by Kelmo7

How many ways can a person select four books, two CDs, and one DVD from ten books, twenty CDs, and five DVDs?

How many different three letter permutations can be formed from the letters in the word clipboard?

How many 3-digit codes using the digits 0 through 9 are possible if repetitions are allowed?


I'm gettng confused. Please help! Thanks!

(10C4) (20C2) (5C1) = ......

9P3 = .....

There are ten digits, not nine!

You need to go back and thoroughly revise the basic formulas and question types.