Stupid Basic Maths Question

Discussion in 'General Off-Topic Chat' started by Lucifer666, Apr 21, 2012.

Apr 21, 2012
  1. Lucifer666
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    Member Lucifer666 all the world needs is me

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    I want to start off by saying that I probably already know the answer to this question from an exercise I didn't even think would exist in my course due to how ridiculously easy it is, but I am beyond sleepy right now and can't force it out of my brain. I'm pulling an all-nighter to finish up some work, and I can no longer think. I've gone mad. I'm aware this is a stupid question.

    So I'm given the formula d=0.0065v^2 + 0.75v
    a) (Some long useless info here) basically translates into find d when v is 50

    What I did:
    d=0.0065(50^2) + 0.75(50)
    d=0.0065(2500) + 37.5
    d=16.25 + 37.5
    d=53.75 m (The unit is metres according to the question)

    That's right, right? I.. no longer have the power to check for myself.

    b) Find v when d is 100 metres
    100=0.0065v^2 + 0.75v
    I uh, don't seem to remember what to do when there are different powers of a variable being added. Look I know this sounds ridiculous, but I need all the help I can get right now. I'm about to collapse.

    I'm gonna try to proceed:
    100=v(0.0065v +0.75)
    100/(0.0065v + 0.75) = v
    Wait what? No, I can't find v in terms of v..

    Thanks in advance gyus

    edit: My bad. I'm aware this should've been in Ask GBAtemp but there would be no spaces between the lines and it all looks squished and uncomfortable to read, so yeah.
     
  2. Thesolcity

    Member Thesolcity Wherever the light shines, it casts a shadow.

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    Herp derp. After doing the problem, you're right.
     
  3. FAST6191

    Reporter FAST6191 Techromancer

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    My usual policy against giving complete answers is in effect.

    a) sure.

    b) Call it a quadratic equation x=(-b+-sqrt(b^2-4ac))/2a

    100=0.0065v^2 + 0.75v

    0 =0.0065v^2 + 0.75v - 100
     
  4. Tom Bombadildo

    Contributor Tom Bombadildo Honk!

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    Damn...FAST beat me to it >.< But yeah, A is INCORRECT I LIED SORRY and for b just subtract 100 and plug it into the quadratic equation.

    To expand upon his suggestion, though, here's what the equation should look like:

    -.75ÂħSQRT.75^2-(4*.0065*-100)
    -----------------------------------------
    2*.0065
     
  5. Lucifer666
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    Member Lucifer666 all the world needs is me

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    This is just my IGCSE maths course, fairly simple. I'm willing to bet this formula isn't real but just made of for the sake of this question. I guess I can type out the entire question for you.
    Warning: Spoilers inside!

    Thanks a lot FAST6191 and Suprgamr232!
    But.. hang on, something's not quite right. I know for a fact that the answers PDF provided with my book says the answer is 110 km/h as an estimate. (I don't trust it, it sometimes has a lot of mistakes)

    Replacing v with 110 in the equation doesn't give me anything close to 100. Either it's another mistake, or I'm just really crapping out at the moment.
     
  6. Wizerzak

    Member Wizerzak Because I'm a potato!

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    I wrote down an answer, then saw it had already been answered. Meh.. no point in writing what has already been written.
     
  7. Tom Bombadildo

    Contributor Tom Bombadildo Honk!

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    B...when I plug in 110 I get 140. So...I think your book is wrong...it's more like...
    Warning: Spoilers inside!

    WARNING: DON'T LOOK IN THE SPOILERS IF YOU DON'T WANT THE ANSWERS
     
  8. ShadowSoldier

    Member ShadowSoldier GBAtemp Guru

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    I read basic.... I have yet to see basic.
     
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