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How I can find U2 here

  1. Jul 1, 2012 #1
    http://store2.up-00.com/June12/Pdb64021.jpg [Broken]

    I will try



    391.4368 + 24.264U2 + 2.2332 / 0.8 = 30.5764/1
    24.461 = 391.436+24.2564U2 + 12.232

    24.461 - 391.436 - 12.232 = 24.2564U2
    U2 = (24.461 - 391.436 - 12.232 ) / 24.2564
    U2 = 15.6
     
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Jul 1, 2012 #2

    Borek

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    Don't ignore parentheses.

    You already made a mistake in your first step. Where did you got 2.2332 from?
     
  4. Jul 1, 2012 #3
    391.4368 + 24.264U2 / 0.8 + (15.290U2) = 30.5764

    Now what will I do

    and this next ..

    391.4368 + 24.264U2 + 2.2332 / 0.8 = 30.5764/1
     
  5. Jul 1, 2012 #4

    Borek

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    Don't ignore parentheses. 391.4368 + 24.264U2 / 0.8 and (391.4368 + 24.264U2) / 0.8 are two different things.

    Apart from lack of parentheses your first step looks OK now. But I still don't know where did you got 2.2332 from.

    [tex]\frac{a+b}c = \frac a c + \frac b c[/tex]
     
  6. Jul 1, 2012 #5
    391.4368 + 24.264U2 / 0.8 + (15.290U2) = 30.5764

    391.4368 + 24.264U2 + (15.290U2) /0.8= 30.5764

    now Is this step is correct ?
     
    Last edited: Jul 1, 2012
  7. Jul 1, 2012 #6

    Borek

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    No, it is wrong. You can't move expressions at random, there are strict rules that you need to follow.

    You are still ignoring parentheses, you are wasting your time and my time.
     
  8. Jul 1, 2012 #7

    vela

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    I think the 2.2332 is supposed to be 12.232, which is what you get by multiplying 15.290 by 0.8.
     
  9. Jul 1, 2012 #8
    So now is my answer is correct or not ... ??
     
  10. Jul 1, 2012 #9

    vela

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    It's kind of hard to follow what you did, so I'd have to say "probably not." First, take the sage Borek's advice and use parentheses. As he noted, a+b/c means something completely different from (a+b)/c. Don't make others guess what you mean when you can write it in a way that's perfectly clear.

    So you're starting off with

    30.581((12.8+0.8u2)/0.8) + 15.290u2 = 30.5764.

    Now show us one step at a time what you're doing. It might help if you explained in words that you're doing each step as well.
     
  11. Jul 1, 2012 #10
    30.581((12.8+0.8u2)/0.8) + 15.290u2 = 30.5764.

    Now I will multiply 30.581 X ((12.8+0.8u2) / 0.8

    = 91.4368 + 24.4648U2 /0.8 + 15.290u2 = 30.5764.

    now I will bring 91.4368 other side
    24.4648U2 /0.8 + 15.290u2 = 30.5764 - 91.4368
    24.4648U2 /0.8 + 15.290u2 = -60.8604
    now I will apply this rule a+b/c to left side
    24.4648U2 + 15.290u2 /0.8 = -60.8604
    Now
    -60.8604 (0.8) = 24.4648U2 + 15.290u2
    u2 = -9.6

    Note : U2 the 2 is not square
     
  12. Jul 1, 2012 #11

    vela

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    How did you get
    $$91.4368 + \frac{24.4648u_2}{0.8} + 15.290u_2 = 30.5764?$$
     
  13. Jul 2, 2012 #12

    Borek

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    I think I know what is going on. You don't ignore parentheses - you have no idea they are necessary. You are consistently making the same error, which suggests you think (1+2)/3=1+2/3. That's incorrect. (1+2)/3=1/3+2/3. Each expression from the sum in the numerator must be divided separately.
     
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