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There are 6 girls and 4 boys. They all participate in a lottery for the places in a line. With which probability will the boys be last in the line and why?
 Mar 18, 2014
 #1
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well, the total possible positions for a group of n objects is n!
! is that number multiplied by all the whole numbers between it and zero. when n is negative, the answer is 1.
ex: 5! = 5*4*3*2*1 = 120

the total positions ("t") for the group = (6+4)! = 10! = 3,528,800
t for the girls ("g") = 6! = 720
t for the boys("b") = 4! = 24

so, the t for b in back and g in front is:
t for g + t for b =
6! + 4! =
720 + 24 =
744

Therefore, I believe the answer to your question would be:
(t for g + t for b) / t for all =
(6! + 4!) / 10! =
(720 + 24) / 3,528,800 =
744 / 3,528,800 =
31 / 14,700

or in percent form:
about a 0.2% chance

P.S. I am not sure about this, because it would take too much time to count it out
 Mar 18, 2014
 #2
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sorry, ! is pronounced factorial
 Mar 18, 2014
 #3
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I think you're REALLY close!!

Since probability isn't my forte, I'm going to take a stab at this one and maybe some sharp cookies like Melody or alan can verify if I'm correct or not!!

Here's the way I thought about this one:

(Ways the girls can be arranged in the front of the line) * (Ways the boys can be arranged at the back of the line) / (Total arrangements possible)

We have (6!) * (4!) / (10!) = 1 / 210 = about .476%

I think we need to multiply the two factorials in the numerator rather than add them because of the Fundamental Counting Principle.
 Mar 18, 2014
 #4
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Ippo:

There are 6 girls and 4 boys. They all participate in a lottery for the places in a line. With which probability will the boys be last in the line and why?



Do you meant that all th girls are first and all th boys are further back?

Probability is not my forte either, but

I think that there are 10!/(6!*4!) = 210 ways of arranging the boys and the girls in a line. I am considering all the girls to be the same and all the boys to be the same since I only care about their gender.

There is only 1 way fo all the boys to come last .

So the probability is 1/210

I'm reasonably sure that is right - now i will compare it to CPhill's answer. YES it is the same. GREAT.

Do you understand Ippo?
 Mar 19, 2014
 #5
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I'm the guest who answered first.

CPhill is right. i thought about it as I was going to bed and I realized I was wrong. sorry, Ippo

the reason is because there are the different girl position with each guy position.
 Mar 19, 2014
 #6
avatar+118677 
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Guest:

I'm the guest who answered first.

CPhill is right. i thought about it as I was going to bed and I realized I was wrong. sorry, Ippo

the reason is because there are the different girl position with each guy position.



Hi guest.
why don't you sign up and join us properly? Here is why you might want to.

http://web2.0calc.com/questions/viewtopic.php?f=2&t=8806&p=18815&hilit=BECOME+A+MEMBER+%3A+Why+would+you+want+to%3F#p18815
 Mar 19, 2014

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