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Assistance required for following

  1. Feb 12, 2007 #1
    assistance required for following plz

    3 questions that have driven me up the wall
    1. The problem statement, all variables and given/known data
    0.5km2 is the same area as
    a)5x10*6m2
    b)5x10*12mm2
    c)5x10*9cm2
    d)5x10*13mm2


    2. Relevant equations
    10*6m=1km2


    3. The attempt at a solution
    0.5x10*6= 500,000 the answer is a) i dont understand what iv done wrong

    q2

    1. The problem statement, all variables and given/known data
    0.04m3 is the same volume as
    a)4x10*6mm3
    b)40dm3
    c)4x105cm3
    d)4x10*2dm3
    2. Relevant equations
    in 1m3=10*9mm
    1x10*9x0.04=4x10*7??
    3. The attempt at a solution
    the answer is a)
    1. The problem statement, all variables and given/known data
    5x10*8mm2 is the same as
    a)500cm2
    b)5x10-4km2
    c)5m2
    d)5x10-2m2
    my workings
    10*6mm=1m2
    1/10*6=1x10-6
    1x10-6x5x10*8=5x10*2
    the answer is d my answer doesnt come as -2 as it should
     
  2. jcsd
  3. Feb 12, 2007 #2
    common guyz i'm dying
     
  4. Feb 12, 2007 #3
    Your solution is correct, if there was a choice for meters squared.

    You'll need to convert that to mm^s, or cm^2 in order to determine which choice is correct. Working within scientific notation makes it easier, i.e rather than .5 km^2, you could write it as .5 * (10^3 m) ^2
    When you square a number with an exponent, you multiply the exponents. Thus, 10^3 squared is 10^6. Thus that equals .5 * 10^6 or in proper scientific notation, 5 * 10^5


    the prefix "kilo" can be replaced with 10^3
    the prefix "centi" can be replaced with 10^-2
    and the prefix "milli" can be replaced with 10^-3

    It might be quicker to just convert everything (the choices) to regular SI units.

    Thus, something like 15 cubic millimeters would look like this
    15 * (10^-3 meters)^3 = 15* 10^-9m^3 or 1.5*10^-8m^3
     
  5. Feb 13, 2007 #4
    if my methods are correcct why are all my answers wrong?
     
  6. Feb 13, 2007 #5

    Gokul43201

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    0.5*10^6 is not 5*10^6

    when you say "the answer is x" are you talking about the choice you believe is the correct answer or are you talking about the answer given by the book. If the latter, they are all wrong. Perhaps you are looking at the wrong part of the answer list?
     
    Last edited: Feb 13, 2007
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