Some clarification

Problem Solving — algebra and arithmetic (GMAT Focus Edition)
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Some clarification

by knight247 » Wed Jun 22, 2011 11:17 am
Been doing probability all day and am a lil confused. I just made the following problem up. How would you go about the following problem? There isn't an OA and hoping someone can solve this problem using both probability and permutation/combination methods with steps explained. Thanks

In a class of 30 students, each of the students were asked to pick an integer between 1 and 20, both inclusive. What is the probability that at least two students have picked up the same integer?
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by Ian Stewart » Wed Jun 22, 2011 1:38 pm
I answered this question here:

www.beatthegmat.com/ds-questions-on-pro ... 85649.html

The answer would be 1, or 100% -- with more students than numbers to pick, two students simply must pick the same number.
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