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No-data

  • 2 years ago

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?

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  1. No-data
    • 2 years ago
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    I'm trying to understand the problem.

  2. No-data
    • 2 years ago
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    I suppose I have to use combinations.

  3. TuringTest
    • 2 years ago
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    me too are we taking out 3 or more?

  4. TuringTest
    • 2 years ago
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    it says 3 but then talks about if 4 are red...

  5. No-data
    • 2 years ago
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    three

  6. TuringTest
    • 2 years ago
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    so for the first are we assuming that 2 of the 3 we are taking out are red or...?

  7. No-data
    • 2 years ago
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    I guess. But if that is the case then I need to use a permutation.

  8. TuringTest
    • 2 years ago
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    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?

  9. TuringTest
    • 2 years ago
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    that's if the balls are unique of course^

  10. No-data
    • 2 years ago
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    No they are not unique.

  11. TuringTest
    • 2 years ago
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    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..:/

  12. No-data
    • 2 years ago
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    Ahhh!

  13. No-data
    • 2 years ago
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    I made a mistake. I copy part of the problem below the one i wanted.

  14. TuringTest
    • 2 years ago
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    that makes sense

  15. No-data
    • 2 years ago
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    b) If all 3 balls are white.

  16. No-data
    • 2 years ago
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    c) If all 3 balls are red=

  17. No-data
    • 2 years ago
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    Sorry =/

  18. TuringTest
    • 2 years ago
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    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

  19. No-data
    • 2 years ago
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    Well at least I'm don't feel alone with the problem =)

  20. No-data
    • 2 years ago
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    I really want to understand this counting techniques.

  21. TuringTest
    • 2 years ago
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    lol I'll be interested to see if someone understands it. Buena suerte!

  22. No-data
    • 2 years ago
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    Thank you!

  23. notsmart
    • 2 years ago
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    mindception

  24. No-data
    • 2 years ago
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    I think you were right TuringTest. They can be called: red_1, red_2, red_3, etc.

  25. No-data
    • 2 years ago
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    In that case I'm selecting 2 out of 7 white balls and 1 out of 3 red balls. So.

  26. No-data
    • 2 years ago
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    \[C(7,2)\cdot C(3,1)\]

  27. TuringTest
    • 2 years ago
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    I though the first was 2 red balls and one white

  28. TuringTest
    • 2 years ago
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    does the order that we pull them out in matter? I guess it should, so my above answer is wrong.

  29. No-data
    • 2 years ago
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    Sorry my bad.

  30. No-data
    • 2 years ago
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    a) If2 balls are white and 1 is red.

  31. No-data
    • 2 years ago
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    The order matters, otherwise I'm lost.

  32. TuringTest
    • 2 years ago
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    yes, otherwise the answer to c) is 1

  33. No-data
    • 2 years ago
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    exactly!

  34. No-data
    • 2 years ago
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    Tu sabes español verdad T

  35. No-data
    • 2 years ago
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    TuringTest

  36. TuringTest
    • 2 years ago
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    well c) should still be the easiest: 3!=6

  37. TuringTest
    • 2 years ago
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    on poco tengo que hacer la tarea para miercoles. no hice nada en lalas vacaciones! estas de acuerdo conmigo acerca parte c) ?

  38. TuringTest
    • 2 years ago
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    un*

  39. No-data
    • 2 years ago
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    Ahh. What do you think about this: I help you with your spanish, and you can help me with my english.

  40. No-data
    • 2 years ago
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    What homework?

  41. TuringTest
    • 2 years ago
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    your english is a lot better than my spanish I'm going to school here taking language classes do you agree about part c?

  42. No-data
    • 2 years ago
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    I think the answer to c) is 1

  43. TuringTest
    • 2 years ago
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    only if the order doesn't matter

  44. TuringTest
    • 2 years ago
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    if it does then it is 6 do you want me to convince you?

  45. No-data
    • 2 years ago
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    Are you sure the order matters?

  46. TuringTest
    • 2 years ago
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    no

  47. No-data
    • 2 years ago
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    Me neither.

  48. TuringTest
    • 2 years ago
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    lol oh man...

  49. No-data
    • 2 years ago
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    I'm going to draw some circles to represent the balls lol

  50. TuringTest
    • 2 years ago
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    me to I guess

  51. No-data
    • 2 years ago
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    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.

  52. No-data
    • 2 years ago
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    I was wondering if I can ask you similar things, and I can help you if you have spanish doubts.

  53. No-data
    • 2 years ago
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    Well even if you can't help me, you can always ask me if you have some doubts.

  54. TuringTest
    • 2 years ago
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    "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

  55. TuringTest
    • 2 years ago
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    thanks by the way

  56. TuringTest
    • 2 years ago
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    I meant 6+5+4+3+2+1=21 ways to select the two white ones

  57. No-data
    • 2 years ago
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    But if the order matters It should be a permutation, so P(7,2) is not equal to 6! I think.

  58. TuringTest
    • 2 years ago
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    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?

  59. No-data
    • 2 years ago
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    Yes! that makes sense!

  60. TuringTest
    • 2 years ago
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    ok then let's see if I have anything for b)...

  61. No-data
    • 2 years ago
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    I thought about selecting 3 whites out of 7, so C(7,3) = 35

  62. TuringTest
    • 2 years ago
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    I agree :D

  63. TuringTest
    • 2 years ago
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    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???

  64. No-data
    • 2 years ago
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    Mmm good question, I'm thinking about it.

  65. TuringTest
    • 2 years ago
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    I don't think I know how to do those.

  66. No-data
    • 2 years ago
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    So you think this problem is done?

  67. No-data
    • 2 years ago
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    That would be great! hehe

  68. TuringTest
    • 2 years ago
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    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.

  69. No-data
    • 2 years ago
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    It is from the book: "College Algebra" written by Sullivan. It seems isa High School book.

  70. TuringTest
    • 2 years ago
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    Then I think we are done :)

  71. No-data
    • 2 years ago
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    Thank you =). And what do you have to do for homework?

  72. TuringTest
    • 2 years ago
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    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.

  73. TuringTest
    • 2 years ago
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    Are you in school?

  74. No-data
    • 2 years ago
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    enamorado means to be in love.

  75. TuringTest
    • 2 years ago
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    awww well that's almost what enamored means

  76. No-data
    • 2 years ago
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    I finished my credits at college, I hope to get my undergraduated grade this year.

  77. TuringTest
    • 2 years ago
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    in what subject?

  78. No-data
    • 2 years ago
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    Mechatronics Engineering

  79. No-data
    • 2 years ago
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    I don't understand quite well what you mean with enamored. Does that word exist in english?

  80. TuringTest
    • 2 years ago
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    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.

  81. TuringTest
    • 2 years ago
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    enamored means obsessed basically, but the word doesn't mean something quite as bad as obsessed

  82. No-data
    • 2 years ago
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    Ahh so you were almost right.

  83. TuringTest
    • 2 years ago
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    or 'awestruck' like I'm enamored by the presence of somebody special so almost...

  84. No-data
    • 2 years ago
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    well I took the basics matehmatics, Algebra, Linear Algebra, Analytic Geometry, Calculus, Probability(Even it seems I didn't), Differential Equations, Complex Analisys, etc.

  85. TuringTest
    • 2 years ago
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    Cool! at UNAM ?

  86. No-data
    • 2 years ago
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    yes, How did you know?

  87. TuringTest
    • 2 years ago
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    because that's where I want to go

  88. TuringTest
    • 2 years ago
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    and you told me you lived in DF

  89. No-data
    • 2 years ago
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    Ohh, want do you want to study there?

  90. No-data
    • 2 years ago
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    What, sorry.

  91. TuringTest
    • 2 years ago
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    Whatever the highest physics I can get into is.

  92. TuringTest
    • 2 years ago
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    what sorry???

  93. No-data
    • 2 years ago
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    I mispelled something, nevermind. So you want a physic's PhD, at UNAM.

  94. TuringTest
    • 2 years ago
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    If I can. I don't know how they feel about gringos getting in though. But UGDL sucks.

  95. No-data
    • 2 years ago
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    So you are studying at UGDL right now.

  96. No-data
    • 2 years ago
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    Why sucks?

  97. TuringTest
    • 2 years ago
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    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.

  98. No-data
    • 2 years ago
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    You mean academic standars, or administrative standars?

  99. TuringTest
    • 2 years ago
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    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...

  100. No-data
    • 2 years ago
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    Well the teachers here are very old hehe.

  101. No-data
    • 2 years ago
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    but there is a good academic level too.

  102. No-data
    • 2 years ago
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    But I think that the best option is at Cinvestav, have you heard of it?

  103. TuringTest
    • 2 years ago
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    no, where's that?

  104. No-data
    • 2 years ago
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    It's has several (places?) on the country, Queretaro, D.F, I'm not sure if Guadalajara.

  105. TuringTest
    • 2 years ago
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    I'll look into it. wrote the name down

  106. No-data
    • 2 years ago
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    There you can find the best academic level in the country.It is difficult to get in.

  107. No-data
    • 2 years ago
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    CINVESTAV

  108. TuringTest
    • 2 years ago
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    brief english lesson: It's has several (places?) on the country It has several locations in the country ^^^correct

  109. No-data
    • 2 years ago
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    Ohh thank you, that is what i meant with my bad english!

  110. No-data
    • 2 years ago
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    There is a Guadalajara's Cinvestav.

  111. TuringTest
    • 2 years ago
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    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?!?!?

  112. No-data
    • 2 years ago
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    Don't worry feel free to write in spanish. That is the best way to learn, by practicing

  113. No-data
    • 2 years ago
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    (there is is wrong?)

  114. TuringTest
    • 2 years ago
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    Thanks for not laughing at me... or at least thanks for not writing lol!! what 'there is'? where

  115. TuringTest
    • 2 years ago
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    oh mine that was to your last comment about there being a school here I went 'there is?" out of surprise

  116. No-data
    • 2 years ago
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    Don't worry =P. I was telling you that there is a Cinvestav located on Guadalajara.

  117. No-data
    • 2 years ago
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    ahh ok hehe

  118. No-data
    • 2 years ago
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    You can take a look here: http://www.cinvestav.mx/posgrado.aspx

  119. No-data
    • 2 years ago
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    Does you gf speaks english?

  120. No-data
    • 2 years ago
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    I even have some of the (admission or entrance?) exams. Let me see..

  121. TuringTest
    • 2 years ago
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    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?

  122. TuringTest
    • 2 years ago
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    cool! entrance exam is the term, what is it in spanish?

  123. No-data
    • 2 years ago
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    Examen de admisión. That is the reason I get confused.

  124. TuringTest
    • 2 years ago
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    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"

  125. TuringTest
    • 2 years ago
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    again sorry for not having accent marks...

  126. No-data
    • 2 years ago
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    Don't worry 70% of mexicans don't know how to use the accent marks.

  127. No-data
    • 2 years ago
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    But is good that you learn how to use them.

  128. TuringTest
    • 2 years ago
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    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.

  129. No-data
    • 2 years ago
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    You mean your roomate at LA?

  130. TuringTest
    • 2 years ago
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    No, here in GDL

  131. No-data
    • 2 years ago
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    Ahh.

  132. TuringTest
    • 2 years ago
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    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 =(

  133. No-data
    • 2 years ago
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    Yeah, it's better to go to sleep. I'm still looking for the entrance exam.

  134. TuringTest
    • 2 years ago
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    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.

  135. No-data
    • 2 years ago
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    Ok, Have a good night, I'm goint to be here tomorrow in case you need some help.

  136. TuringTest
    • 2 years ago
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    I may have to take you up on that, thanks! goodnight No-Data.

  137. No-data
    • 2 years ago
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    to what?

  138. No-data
    • 2 years ago
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    what does it means to take something up?

  139. TuringTest
    • 2 years ago
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    "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.

  140. TuringTest
    • 2 years ago
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    or just, 'I might take you up on that' for short

  141. No-data
    • 2 years ago
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    Ahh thanks!

  142. No-data
    • 2 years ago
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    Well is difficult to learn that in a book or with google traslator. thank you so much. And have a good night again

  143. TuringTest
    • 2 years ago
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    yeah expressions are tricky... goodnight :D

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