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## anonymous 3 years ago Find the probability of randomly selecting three science books and four history books from a box containing five science books and six history books.

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1. hba

5C3+6C4=

2. anonymous

@hba Why would we be adding in this case? It's not "three science books OR four history books"

3. hba

my bad :(

4. anonymous

No problem, I wasn't even sure that you were wrong, I was just confused.

5. anonymous

My guess is $$\binom{5}{3} \times \binom{6}{4} \div \binom{11}{7}$$ It's assuming they meant to say "choosing 7 books randomly". Because otherwise it could be 100% or even 0%.

6. hartnn

^ thats correct.

7. hba

The answer would be 5/11 then ?

8. anonymous

If I am correct then wolfram agrees: http://www.wolframalpha.com/input/?i=%285+choose+3%29+*+%286+choose+4%29++%2F+%2811+choose+7%29

9. hba

hmm,I am really sorry about the mistake i made :/

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