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Mathematics 22 Online
OpenStudy (anonymous):

How many 4-letter words with at least one consonant can be constructed from the letters A B C D and E? It does not have to be a word in the English language and letters may repeat.

OpenStudy (anonymous):

Let me write what I thought.

OpenStudy (anonymous):

I have four spaces: __ __ __ __

OpenStudy (anonymous):

I can choose any of the letters of the alphabet on the first position, so:

OpenStudy (anonymous):

26 __ __ __

OpenStudy (anonymous):

Now, I can choose 5 letters (the vowels on each on the remaining spaces)

OpenStudy (anonymous):

26*5*5*5

OpenStudy (anonymous):

And I can do this in four different ways..

OpenStudy (anonymous):

26*5*5*5*4

OpenStudy (across):

Why are you using the whole alphabet?

OpenStudy (anonymous):

I know this was posted before but I could not understand it. =/

OpenStudy (anonymous):

HINT: Whenever there is "at-least" think about using mutual-inclusion-exclusion.

OpenStudy (anonymous):

Because you can choose any letter for the first position @across

OpenStudy (across):

Oh, I was reading the OP.

OpenStudy (anonymous):

I was doing something like that yesterday, and I don't see the relationship. @FFM

OpenStudy (anonymous):

What is exactly mutual-inclusion-exclusion?

OpenStudy (anonymous):

How many 4-letter words with at least one consonant can be constructed from the letters A B C D and E? What is the answer ?

OpenStudy (anonymous):

My answer is 13000

OpenStudy (anonymous):

I mean the right answer.

OpenStudy (anonymous):

Mmm I don't know.

OpenStudy (anonymous):

Well, calculated 609

OpenStudy (anonymous):

But I don't understand her reasoning.

OpenStudy (anonymous):

I believe the answer should be \(5^5 - 2^5\) using only the given letters.

OpenStudy (anonymous):

Ok, now I have 3 different answers. I think I'll better read about what you said to me.

OpenStudy (anonymous):

and assuming that the letters are repeating.

OpenStudy (anonymous):

Because I'm very lost with this counting techniques

OpenStudy (anonymous):

Yes, they can be repeated.

OpenStudy (anonymous):

hey remeber me the one u reported yesterday snowball

OpenStudy (across):

FFM, I believe you meant to say \(5^4-2^4\) since it's a 4-letter word.\[\]

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