Howdy!
Please I need explanation to the approach of the probability question below.
"There are 27 students on the college debate team. what is the probability that at least 3 of them have their birthday in the same month?"
Source: Page 433 of Barron's New GRE 19th edition.
The answer given is 1, however, I guess the answer should be
1-2/27 = 25/27.
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- kwame.appau
- Prospective Students
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- Joined: Sat Jan 05, 2013 6:49 am
- tommywallach
- Manhattan Prep Staff
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- Joined: Thu Mar 31, 2011 11:18 am
Re: Probability
Hey Kwame,
If you have 12 people, the most evenly distributed they could be would place 1 person in each month. If there were 24 people, the most evenly distributed they could be would place two people in each month. But at that point, if you add another person, they have to join a month that already has two people. There is no way to distribute more than 24 people in 12 months and not have at least one month with three people in it.
-t
If you have 12 people, the most evenly distributed they could be would place 1 person in each month. If there were 24 people, the most evenly distributed they could be would place two people in each month. But at that point, if you add another person, they have to join a month that already has two people. There is no way to distribute more than 24 people in 12 months and not have at least one month with three people in it.
-t
- kwame.appau
- Prospective Students
- Posts: 35
- Joined: Sat Jan 05, 2013 6:49 am
Re: Probability
Oh I see. Thanks very much. So it means one need not to necessarily use formula to solve it?
- tommywallach
- Manhattan Prep Staff
- Posts: 1917
- Joined: Thu Mar 31, 2011 11:18 am
Re: Probability
More than that, you can't use a formula to solve this one. This happens surprisingly often on the test, so never turn off your "logical" brain and resort to trying to "solve" everything.
Good luck!
-t
Good luck!
-t
4 posts Page 1 of 1