math help...

Discussion in 'General Discussion' started by Lumpy, Jun 7, 2008.

  1. Lumpy

    Lumpy Taylor Swift Actionmaster Super Mod

    Joined:
    Sep 3, 2002
    Posts:
    18,924
    News Credits:
    29
    Trophy Points:
    292
    Likes:
    +33
    okay, so i've got my big math test tomorrow (to be a middle school math teacher) and my brain is fried, and apparently i don't know how to do some stuff... if anyone can offer advice, that'd be great... i've been training for my summer job the past few days, and i think my brain is just fried, so i know some of this, just cant remember it all...anyone who can offer any help, or even just words of encouragement (i'm pretty much freaking out) i would really appreciate it...

    btw, if anyone wants to see the sample questions, here ya go...

    Lumpy's dreaded math test study guide of worthlessness

    of note, the questions i feel the most lost on are 4-7, and 10...

    ps, i'm bloody exhausted, so i will check this again in the morning...thanks again...
     
  2. undertaker

    undertaker Deadman's Disciple

    Joined:
    Jan 23, 2004
    Posts:
    851
    Trophy Points:
    156
    Likes:
    +0
    Like you said, if you're fried, it would all start to turn into garble. I'm sure some sleep will work wonders.

    #5. It's all about similar triangles. Triangle ABE and Triangle ACD are similar triangles, so the ratios of the side lengths should be equal (ie, BE/CD = AE/AD = AB/AC). You'll have to solve for AB. We have:
    AB/(AB + 30) = 60/80. Reduce and solve... AB/(AB + 30) = 3/4. [Cross-multiply to have 4(AB) = 3(AB+30).] Ultimately, AB = 90 m


    #6. It's all about volumes and "scaling." First, get the volume of the cylinder: A = pi*(r^2)*h = 96(pi) cubic cm.
    After 1.5 hours, the cylinder is 3/4 full... meaning 1/4 empty (since we need to focus on rate of loss of water). So, here's the "scaling" part. In 1.5 hours (ie, 90 minutes, since all the answers are in minutes). We just want to see how much water is lost per minute: We lost 1/4 of the volume, 24(pi) cubic cm, in 90 minutes... 24(pi) cubic cm / 90 minutes = 4(pi) cubic cm / 15 minutes.

    4(pi)/15 cubic cm per minute (answer B)


    #7. The key to this is terminology. Mean = average.
    Just add up the number of CDs owned by all the students and divide by the number of students.
    mean = 65/24 which is approximately 2.71


    #10. To keep this short, my suggestion is to determine which answer works rather than to try to determine the actual function and see which matches your result. In 5 hours, the original set of 10,000 is supposed to double. So, if t = 5, the function should equal 20,000. Only A does that when you plug in t = 5.


    #4. Saved this for last as it's more involved than the others (at least my explanation will be). How did I do it? Write a system of equations.
    You have three unknowns, so you'll never really solve for all the variables. We have the weight of the salt (which does not change), s, and TWO water weights, w and x, w being the initial weight of the water and x being the weight of the evaporated water.
    The equations -
    1. w = .8(w + s) [Initially, the salt water solution was 80% water by weight, so w was equal to 80% of the TOTAL weight.]
    2. w - x = .4 (w - x + s) [Water has evaporated, so the weight of the remaining water is w - x. The weight of the remaining water is 40% of the TOTAL weight which now consists of the salt and the REMAINING water. The key here: After evaporation, we have w-x for the weight of the water, so this equation follows the form of the other one except we need w-x instead of having just w.]

    Time to solve this. We need to determine the ratio of the final weight of the water to the initial weight of the water. The final weight was w-x, and the initial was x... we need to evaluate the fraction (w-x)/w. We need to "solve" for w and x in order to do this (technically, we don't need to solve for x and w specifically, but this may be the easier way). So, solve equation 1 for w (it's easier to start there). You get w = 4s. Substitute that into equation 2, and then solve for x. After substituting, we have 4s - x = .4(4s - x + s) --> 4s - x = 2s - .4x. Solve for x and get x = (10/3)s.
    We now have all our information. (w-x)/w = (4s - 10/3s)/4s = [(2/3)s/4s] = (2/3)/(4) = (2/3) x (1/4) = 2/12 = 1/6.
    Answer A.
     
  3. CdnShockwave

    CdnShockwave The Prince of Poses TFW2005 Supporter

    Joined:
    Jul 4, 2002
    Posts:
    10,548
    Trophy Points:
    266
    Likes:
    +0
    My head exploded sending gooey bits of brain, bone, and teeth everywhere at the mere mention of the word "math"
     
  4. Deceptikitty

    Deceptikitty all about the hasubandos

    Joined:
    Nov 5, 2007
    Posts:
    4,163
    Trophy Points:
    151
    Likes:
    +0
    Same. :( 
     
  5. CdnShockwave

    CdnShockwave The Prince of Poses TFW2005 Supporter

    Joined:
    Jul 4, 2002
    Posts:
    10,548
    Trophy Points:
    266
    Likes:
    +0
    That's hot.
     
  6. omega knight

    omega knight Chibi lancelot launch

    Joined:
    Mar 7, 2006
    Posts:
    1,370
    News Credits:
    1
    Trophy Points:
    161
    Likes:
    +1
    Okay dude, First off I just got out of middle school this year and, there are gonna be very few kids who actually care what your gonna say just a heads up. Don't get down you can do it!
     
  7. Sideways

    Sideways Banned

    Joined:
    May 17, 2006
    Posts:
    2,432
    Trophy Points:
    186
    Likes:
    +0
    my brains hert..
     
  8. Prowl_Delta_31

    Prowl_Delta_31 Eating your donuts

    Joined:
    Mar 30, 2007
    Posts:
    2,640
    News Credits:
    1
    Trophy Points:
    151
    Likes:
    +1
    And in that lies one of the many problems with kids these days.
     
  9. omega knight

    omega knight Chibi lancelot launch

    Joined:
    Mar 7, 2006
    Posts:
    1,370
    News Credits:
    1
    Trophy Points:
    161
    Likes:
    +1
    no shit XD I wish they would still give spakkins ( no k.a and jux this is not a plan for u two to get endless enjoyment ) to kids it would solve a lot of problems.
     
  10. Blunticon

    Blunticon The Oddjob

    Joined:
    May 18, 2006
    Posts:
    3,685
    Trophy Points:
    186
    Likes:
    +0
    The best time to study is before you sleep, you will retain more. Most of the time you learn something you forget half of it before the day is gone. Thats what dreams are for, they are rerouting your info that you learned.
     
  11. Vector Sigma

    Vector Sigma <b><i><font color=FFFF00>Crazy Colon Burner!!!!</b Veteran

    Joined:
    Jul 2, 2002
    Posts:
    6,510
    Trophy Points:
    221
    Likes:
    +0
    Best of luck looks like undertaker has you covered on how to work through the ones you weren't too sure on. I hope it goes really wellfor you :) ...
     
  12. Bryan

    Bryan ΜΟΛΩΝ ΛΑΒΕ

    Joined:
    Sep 8, 2005
    Posts:
    9,020
    Trophy Points:
    211
    Likes:
    +0
    I made it through Calc II back in my previous attempt at an education, but now, I expect to do exactly one specific algebra problem for the rest of my life.

    I'm gonna give the test a shot later, though.
     
  13. Lumpy

    Lumpy Taylor Swift Actionmaster Super Mod

    Joined:
    Sep 3, 2002
    Posts:
    18,924
    News Credits:
    29
    Trophy Points:
    292
    Likes:
    +33
    thanks guys, especially undertaker...that totally makes sense...7 was bloody stupid easy...i should had that one... 4 is still confusing me, so i'm gonna reread your description a couple more times....
     
  14. Lumpy

    Lumpy Taylor Swift Actionmaster Super Mod

    Joined:
    Sep 3, 2002
    Posts:
    18,924
    News Credits:
    29
    Trophy Points:
    292
    Likes:
    +33
    last bit of help, if anyone can help me with number 9...i still cant figure that one out...
     
  15. Aldude

    Aldude Automorph

    Joined:
    May 4, 2007
    Posts:
    65
    Trophy Points:
    46
    Likes:
    +0
    #9
    You need both terms to have denominator the same before you can add them together.
    Multiply the left hand one by (x+3) on the top and bottom, then multiply the right hand one by (x+4) on the top and bottom. So both terms have (x+3)(x+4) on the bottom. So just multiply out everything and then add them together.

    Edit: I think the answer is D. - i haven't fully worked it out, but at a quick glance, it looks like D
     

Share This Page