anonymous
  • anonymous
An urn contains 7 white balls and 3 red balls. Three balls are selected. In how many ways can the 3 balls be drawn from the total of 10 balls a) If 2 balls are red? b) If 3 balls are red and 2 are white? c) If at leas 4 are red balls?
Mathematics
jamiebookeater
  • jamiebookeater
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anonymous
  • anonymous
I'm trying to understand the problem.
anonymous
  • anonymous
I suppose I have to use combinations.
TuringTest
  • TuringTest
me too are we taking out 3 or more?

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TuringTest
  • TuringTest
it says 3 but then talks about if 4 are red...
anonymous
  • anonymous
three
TuringTest
  • TuringTest
so for the first are we assuming that 2 of the 3 we are taking out are red or...?
anonymous
  • anonymous
I guess. But if that is the case then I need to use a permutation.
TuringTest
  • TuringTest
that's what I'm confused on if the first question is asking 'we draw 3 balls, how many ways can we do this of two of the three we take out are red?' then I would say 3 ways to select red balls 7 ways to select the white ball 3*7=21 but then what about the rest?
TuringTest
  • TuringTest
that's if the balls are unique of course^
anonymous
  • anonymous
No they are not unique.
TuringTest
  • TuringTest
oh, well then I'm really confused. I especially don't see how you can have 4 red balls when it says there are 3 in the urn..:/
anonymous
  • anonymous
Ahhh!
anonymous
  • anonymous
I made a mistake. I copy part of the problem below the one i wanted.
TuringTest
  • TuringTest
that makes sense
anonymous
  • anonymous
b) If all 3 balls are white.
anonymous
  • anonymous
c) If all 3 balls are red=
anonymous
  • anonymous
Sorry =/
TuringTest
  • TuringTest
well I still don't get the question. if it is as I said above and the balls are not unique, then...no I'm lost, sorry
anonymous
  • anonymous
Well at least I'm don't feel alone with the problem =)
anonymous
  • anonymous
I really want to understand this counting techniques.
TuringTest
  • TuringTest
lol I'll be interested to see if someone understands it. Buena suerte!
anonymous
  • anonymous
Thank you!
anonymous
  • anonymous
mindception
anonymous
  • anonymous
I think you were right TuringTest. They can be called: red_1, red_2, red_3, etc.
anonymous
  • anonymous
In that case I'm selecting 2 out of 7 white balls and 1 out of 3 red balls. So.
anonymous
  • anonymous
\[C(7,2)\cdot C(3,1)\]
TuringTest
  • TuringTest
I though the first was 2 red balls and one white
TuringTest
  • TuringTest
does the order that we pull them out in matter? I guess it should, so my above answer is wrong.
anonymous
  • anonymous
Sorry my bad.
anonymous
  • anonymous
a) If2 balls are white and 1 is red.
anonymous
  • anonymous
The order matters, otherwise I'm lost.
TuringTest
  • TuringTest
yes, otherwise the answer to c) is 1
anonymous
  • anonymous
exactly!
anonymous
  • anonymous
Tu sabes español verdad T
anonymous
  • anonymous
TuringTest
TuringTest
  • TuringTest
well c) should still be the easiest: 3!=6
TuringTest
  • TuringTest
on poco tengo que hacer la tarea para miercoles. no hice nada en lalas vacaciones! estas de acuerdo conmigo acerca parte c) ?
TuringTest
  • TuringTest
un*
anonymous
  • anonymous
Ahh. What do you think about this: I help you with your spanish, and you can help me with my english.
anonymous
  • anonymous
What homework?
TuringTest
  • TuringTest
your english is a lot better than my spanish I'm going to school here taking language classes do you agree about part c?
anonymous
  • anonymous
I think the answer to c) is 1
TuringTest
  • TuringTest
only if the order doesn't matter
TuringTest
  • TuringTest
if it does then it is 6 do you want me to convince you?
anonymous
  • anonymous
Are you sure the order matters?
TuringTest
  • TuringTest
no
anonymous
  • anonymous
Me neither.
TuringTest
  • TuringTest
lol oh man...
anonymous
  • anonymous
I'm going to draw some circles to represent the balls lol
TuringTest
  • TuringTest
me to I guess
anonymous
  • anonymous
Well Hero sometimes help with my english. Hi write something to him and he says: "No, you can write that in this way". I'm very grateful to him, but I'm ashamed that I can't not help him with something I know.
anonymous
  • anonymous
I was wondering if I can ask you similar things, and I can help you if you have spanish doubts.
anonymous
  • anonymous
Well even if you can't help me, you can always ask me if you have some doubts.
TuringTest
  • TuringTest
"can't not help him" should be "can't help him" and I your the first mexican I've met who actually wants to help. All my friends just make fun of me. anyhow I see 6! ways te select 2 white balls out of 7
TuringTest
  • TuringTest
thanks by the way
TuringTest
  • TuringTest
I meant 6+5+4+3+2+1=21 ways to select the two white ones
anonymous
  • anonymous
But if the order matters It should be a permutation, so P(7,2) is not equal to 6! I think.
TuringTest
  • TuringTest
no, I was wrong about that sorry my working theory is that the order does not matter and that there are 21 ways to select 2 white balls out of seven, and 3 ways to select the red one for each of those, so 21*3=63 ways for part a) make any sense?
anonymous
  • anonymous
Yes! that makes sense!
TuringTest
  • TuringTest
ok then let's see if I have anything for b)...
anonymous
  • anonymous
I thought about selecting 3 whites out of 7, so C(7,3) = 35
TuringTest
  • TuringTest
I agree :D
TuringTest
  • TuringTest
well so then the answer is a)63 b)35 c)1 IF the order of selection does not matter. so what if it does???
anonymous
  • anonymous
Mmm good question, I'm thinking about it.
TuringTest
  • TuringTest
I don't think I know how to do those.
anonymous
  • anonymous
So you think this problem is done?
anonymous
  • anonymous
That would be great! hehe
TuringTest
  • TuringTest
I think you probably know better. Where did you get this problem? Does it seem like it should be so difficult as to have to consider order? That seems extraneous to me, unless you have an advanced combinatorics book or something.
anonymous
  • anonymous
It is from the book: "College Algebra" written by Sullivan. It seems isa High School book.
TuringTest
  • TuringTest
Then I think we are done :)
anonymous
  • anonymous
Thank you =). And what do you have to do for homework?
TuringTest
  • TuringTest
I'm trying to figure out what my girlfriend just texted me... chulos ojos de perrito enamorado not sure what enamorado means, but it must be enamored, eh? I have to do adverbs, practice past participle, negations, and... I don't know. A lot. I should have done it over break.
TuringTest
  • TuringTest
Are you in school?
anonymous
  • anonymous
enamorado means to be in love.
TuringTest
  • TuringTest
awww well that's almost what enamored means
anonymous
  • anonymous
I finished my credits at college, I hope to get my undergraduated grade this year.
TuringTest
  • TuringTest
in what subject?
anonymous
  • anonymous
Mechatronics Engineering
anonymous
  • anonymous
I don't understand quite well what you mean with enamored. Does that word exist in english?
TuringTest
  • TuringTest
Dang, what math did you have to take for that? I would think a lot, but it seems like you don't know too much more than me.
TuringTest
  • TuringTest
enamored means obsessed basically, but the word doesn't mean something quite as bad as obsessed
anonymous
  • anonymous
Ahh so you were almost right.
TuringTest
  • TuringTest
or 'awestruck' like I'm enamored by the presence of somebody special so almost...
anonymous
  • anonymous
well I took the basics matehmatics, Algebra, Linear Algebra, Analytic Geometry, Calculus, Probability(Even it seems I didn't), Differential Equations, Complex Analisys, etc.
TuringTest
  • TuringTest
Cool! at UNAM ?
anonymous
  • anonymous
yes, How did you know?
TuringTest
  • TuringTest
because that's where I want to go
TuringTest
  • TuringTest
and you told me you lived in DF
anonymous
  • anonymous
Ohh, want do you want to study there?
anonymous
  • anonymous
What, sorry.
TuringTest
  • TuringTest
Whatever the highest physics I can get into is.
TuringTest
  • TuringTest
what sorry???
anonymous
  • anonymous
I mispelled something, nevermind. So you want a physic's PhD, at UNAM.
TuringTest
  • TuringTest
If I can. I don't know how they feel about gringos getting in though. But UGDL sucks.
anonymous
  • anonymous
So you are studying at UGDL right now.
anonymous
  • anonymous
Why sucks?
TuringTest
  • TuringTest
Just two classes. Between that, moving here, and language I'm busy. It's just a bad system in my opinion. They don't have high enough standards.
anonymous
  • anonymous
You mean academic standars, or administrative standars?
TuringTest
  • TuringTest
academic was what I meant, but I'm sure administrative as well. My girlfriend had 4/6 of her graphic design teachers be about 25 years old. I'm almost that old! Not exactly tenure...
anonymous
  • anonymous
Well the teachers here are very old hehe.
anonymous
  • anonymous
but there is a good academic level too.
anonymous
  • anonymous
But I think that the best option is at Cinvestav, have you heard of it?
TuringTest
  • TuringTest
no, where's that?
anonymous
  • anonymous
It's has several (places?) on the country, Queretaro, D.F, I'm not sure if Guadalajara.
TuringTest
  • TuringTest
I'll look into it. wrote the name down
anonymous
  • anonymous
There you can find the best academic level in the country.It is difficult to get in.
anonymous
  • anonymous
CINVESTAV
TuringTest
  • TuringTest
brief english lesson: It's has several (places?) on the country It has several locations in the country ^^^correct
anonymous
  • anonymous
Ohh thank you, that is what i meant with my bad english!
anonymous
  • anonymous
There is a Guadalajara's Cinvestav.
TuringTest
  • TuringTest
I wish you could just give me little tips like that in spanish, but I've only been taking classes for 2 1/2 months. It'll be awhile befor I'm fluent :( -there is?!?!?
anonymous
  • anonymous
Don't worry feel free to write in spanish. That is the best way to learn, by practicing
anonymous
  • anonymous
(there is is wrong?)
TuringTest
  • TuringTest
Thanks for not laughing at me... or at least thanks for not writing lol!! what 'there is'? where
TuringTest
  • TuringTest
oh mine that was to your last comment about there being a school here I went 'there is?" out of surprise
anonymous
  • anonymous
Don't worry =P. I was telling you that there is a Cinvestav located on Guadalajara.
anonymous
  • anonymous
ahh ok hehe
anonymous
  • anonymous
You can take a look here: http://www.cinvestav.mx/posgrado.aspx
anonymous
  • anonymous
Does you gf speaks english?
anonymous
  • anonymous
I even have some of the (admission or entrance?) exams. Let me see..
TuringTest
  • TuringTest
Yeah, which has really slowed me down. She has no patience. Everytime I ask her something she says 'that's stupid, why would you ask that?' I will be looking into that school here, I kinda like Guadalajara, and after living in LA for 12 years I don't really want to move to DF more expensive to, right?
TuringTest
  • TuringTest
cool! entrance exam is the term, what is it in spanish?
anonymous
  • anonymous
Examen de admisión. That is the reason I get confused.
TuringTest
  • TuringTest
right, I tried to say pagar atencion once, I got laughed at, but that's what it is in english "pay attention" not "put attention"
TuringTest
  • TuringTest
again sorry for not having accent marks...
anonymous
  • anonymous
Don't worry 70% of mexicans don't know how to use the accent marks.
anonymous
  • anonymous
But is good that you learn how to use them.
TuringTest
  • TuringTest
My roomate spoke spanish at home all his life and was born in DF, but I correct him on things sometimes because I'm learning spanish formally. He never did that.
anonymous
  • anonymous
You mean your roomate at LA?
TuringTest
  • TuringTest
No, here in GDL
anonymous
  • anonymous
Ahh.
TuringTest
  • TuringTest
I think we have the same time zone, right? I know it's not that late, but I think I should try to sleep. I have to do 2 weeks worth of homework tomorrow =(
anonymous
  • anonymous
Yeah, it's better to go to sleep. I'm still looking for the entrance exam.
TuringTest
  • TuringTest
Thanks for the info on Cinvestav, I'll look into it. And looking for the exam. If you find it I'd be curious to hear what it has.
anonymous
  • anonymous
Ok, Have a good night, I'm goint to be here tomorrow in case you need some help.
TuringTest
  • TuringTest
I may have to take you up on that, thanks! goodnight No-Data.
anonymous
  • anonymous
to what?
anonymous
  • anonymous
what does it means to take something up?
TuringTest
  • TuringTest
"to take someone up on an offer" I said I'd have to take you up on your offer, meaning I may ask you for help with spanish.
TuringTest
  • TuringTest
or just, 'I might take you up on that' for short
anonymous
  • anonymous
Ahh thanks!
anonymous
  • anonymous
Well is difficult to learn that in a book or with google traslator. thank you so much. And have a good night again
TuringTest
  • TuringTest
yeah expressions are tricky... goodnight :D

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