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Homework Help.

Discussion in 'Off Topic' started by death2all110, Aug 23, 2012.

  1. death2all110

    death2all110 Android Expert
    Thread Starter

    Okay, homework help, I'm not thinking clearly apparently,because I keep swearing up and down its wrong, so here goes....
    I got 60.5mL of 5% acid.

    But I think I might be wrong. Any input?

    To prove I actually tried working it out and I'm not just trying to get you guys to solve something for me...

    Obviously my handwriting sucks....

    Member243850 likes this.

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  2. Kelmar

    Kelmar Done by choice

    I could be mistaken...

    but wouldn't the correct equation would be:

    .05x + .2(60) = .1(x+60)
    death2all110 and Member243850 like this.
  3. Member243850

    Member243850 Guest

    Well done,

    NEVER be afraid to ask for help! :)

    Seriously well done it takes a man to do ask for help and yes I can see you are trying too so well done!


    Hmmm okay that question is not very well worded but lets ignore that for the moment and give it a bash.

    From what I can see, the total amount of acid is 60 ml right?

    Or am I maybe wrong?

    Lets go!




    So you say this is how we do it right?

    Lets say you are right with your current way of thinking ;)

    Here is the solution but you need to tell me how I got there is it a deal? ;)


    I am glad to see you are doing maths... most children for some strange reason are scared of doing it.

    Well done!!
    ocnbrze and death2all110 like this.
  4. Member243850

    Member243850 Guest



    I have the WORST hand writing in the world! ;)

    So don't feel down about that mindless detail! :)
  5. Stuntman

    Stuntman Android Expert

    My chemistry may be a bit off here, but I think my math is right:

    60mL of 20% solution is 12 mL of Acid and 48 mL of Water. (By Acid, I mean 100% acid)

    Let Y be the total amount of the final mixture.

    Y mL of 10% solution is Y/10 mL Acid and 9Y/10 mL Water.

    Let X be the total amount of 5% solution.

    X mL of 5% solution is X/20 mL Acid and 19X/20 mL Water.

    You get these two linear equations:

    12 mL Acid + X/20 mL Acid = Y/10 mL Acid

    48 mL Acid + 19X/20 mL Acid = 9Y/10 mL Acid

    Take out the mL Acid and you get

    12 + X/20 = Y/10 => 120 + X/2 = Y
    48 + 19X/20 = 9Y/10

    By substituting Y with 120 + X/2 in the second equation, you are left with X only in one equation.

    Solve and X = 120 mL.
    death2all110 and Member243850 like this.
  6. Member243850

    Member243850 Guest

    Hmm you see the question is worded very badly or is it just me? :thinking:

    I don't 200% understand what the question is asking for as it is very very ambiguous.

    At least to me it is.

    The question itself is a problem.

    If 60 ml = 100%

    Just for arguments sake.

    So if 60 ml = 100%

    then 10% = 6 milliliters

    Am I correct here right guys?


    if 6 = 10%

    then surely

    3 milliliters = 5%


    You see the question is an issue here to me at least it is :)
  7. Kelmar

    Kelmar Done by choice

    I'm pretty sure they want to know how much (variable) 5% acid would need mixed with (fixed 60mL) 20% acid to make 10% acid. ;)
    Member243850 likes this.
  8. Member243850

    Member243850 Guest

    Hmmm I am not 100% sure.

    I have got a slight feeling it is not worded right.

    Hell I could be totally wrong though :)
  9. death2all110

    death2all110 Android Expert
    Thread Starter

    See that's why I'm getting stuck. Unfortunately my teacher is german, so german is her native language, and she has a strong accent. So her homework assignment is oddly worded and I've suffered through most of it. I think kelmar's 1st reply is right though, and my math is definitely off. Ill take another crack at it.. Thanks!

    Took another crack at it. and got a vastly different answer! Looks to be the same as Stuntman's


    Picture of my math, with *somewhat* better writing....

  10. Kelmar

    Kelmar Done by choice

    FWIW, that's the answer I got and it makes sense (to me) too

    Working it backwards and plugging the solution into the equation makes sense when you do the math.
    death2all110 likes this.
  11. death2all110

    death2all110 Android Expert
    Thread Starter

    Glad I came here, I would have looked stupid turning in my original answer! xD Especially when I can't re-create it! Funny how my ORIGINAL work was missing the X after 0.05 and thus drastically changing the answer. Going back to my original work, and replacing 0.05 with 0.05x and doing the equation that way yields the same answer.
  12. Kelmar

    Kelmar Done by choice

    Hopefully it's right!

    Otherwise we'll all look stupid hiding behind our anonymous avatars. :D
  13. Stuntman

    Stuntman Android Expert

    In your table, the Solution 1 Acid entry should be 0.05X, not 0.5X.
    death2all110 likes this.
  14. TJGoSurf

    TJGoSurf Android Expert

    Looks like everything is all solved here.

    College algebra? Those days were fun. Just think you'll get to stare at this one day:

  15. Kelmar

    Kelmar Done by choice

    I remember those days! Too bad (or lucky me) I don't have to do stuff like that anymore. :D
  16. TJGoSurf

    TJGoSurf Android Expert

    Math is the greatest thing ever. Those who do not know it are doomed to repeat it. Or was that history? Seems to work for both.

    I met a friend at a bar. He teaches a basic math class at the community college. We were hammered and grading papers. Alcohol may inhibit the thinking process but I can't mess up questions like '5-8'.
  17. Kelmar

    Kelmar Done by choice

    What I like about math is that there is ALWAYS right answer. You don't have to worry about which version of "there" to use or about punctuation. It's cut, dry and right or wrong! :)
    9to5cynic likes this.
  18. TJGoSurf

    TJGoSurf Android Expert

    I'll show you!

    1*2=2*2 Multiply both sides by 2
    2-3=4-3 Subtract 3 from both sides
    (-1)^2=1^2 Square both sides

    As you can see 1=2.
  19. Kelmar

    Kelmar Done by choice

    Ah... those are and were the best :D
  20. TJGoSurf

    TJGoSurf Android Expert

  21. Kelmar

    Kelmar Done by choice

    Hadn't seen that one!
  22. 9to5cynic

    9to5cynic Android Expert

    I was never really good at math, I was just okay, but it was always one of my favorite subjects because that's the thing: no matter what, there is a definitive answer. It's not like other subjects where answers are up to interpretations. :D
  23. TJGoSurf

    TJGoSurf Android Expert


    Find the particular solution of

    given that when x=0,y=2.
  24. death2all110

    death2all110 Android Expert
    Thread Starter

    Thanks I'll be sure to fix that xD

    And thanks to everyone else for the help!
  25. Stuntman

    Stuntman Android Expert

    I love math. I actually miss it as now that I'm out of school, I don't get very many opportunities to do much math. I jumped at the chance when I saw this thread.

    There's not necessarily a definitive answer. There do exist unsolvable problems. Such problems are more primarily in the realm of Computer Science. In math, an unsolvable problem would be finding an equation for solving the zeros of a polynomial of degree 5 or higher. For polynomials of degree 2, you have the quadratic equation which is well known. There is no answer for a polynomial of degree 5 or higher.

    You're very welcome. I had a lot of fun using my high school algebra again.

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