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More SAT problems

  1. Jan 2, 2007 #1
    Mind helping me out on one of these problems?

    If 10,000 microns=1 cent. and 100,000,000 angstrom units=1 cent.
    how many angstrom units equal 1 micron?

    A. 0.00000000000000001 or something, but you know it is wrong

    B) 0.0001

    C) 10,000

    D) 100,000

    E) 1,000,000,000,000

    At first, I chose B) because I divided microns by angstroms. So how do you solve this kind of problem?? These are usually the problems that I have difficulty on. I know I'm dumb. xD

    Hey if anyone here has the BlueBook then can you turn to page 337. I have a question on #6. I got the right answer the first time because: Since all triangles are .5bh and the base is all the same (radius line seg. OX), then all you would need to consider is the height right?

    Please answer this: Do you find all triangles' area from the equation 1/2bh?? Does it apply to any type of triangle? You find the height from the vertex of a corner of a triangle correct? and it has to be perpendicular to the base?

    Thanks a lot guys!
  2. jcsd
  3. Jan 2, 2007 #2
    I'm sure you can solve the first problem if you think a little. As for the problem with the triangles in the circle, yes, you are correct. The base is always equal to radius, so all you need to consider is smallest height.
  4. Jan 2, 2007 #3

    D H

    Staff: Mentor

    You should also know C,D, and E are wrong right away because they are greater than 1 and because it takes many more angstroms to make one cm than microns. The only possible answer, at a glance, is B. Quickly ruling out the wrong answers without doing the work is the best way to take these stupid tests.
  5. Jan 2, 2007 #4
    I think we're getting confused here... a micron is more than 1 angstrom.
  6. Jan 2, 2007 #5
    Umm.. The question asks how many angstroms make 1 micron, and since it takes many more angstroms than microns to make a cm then the number of angstroms in a micron should obviously be more than 1 thus ruling out choice B.
  7. Jan 2, 2007 #6

    D H

    Staff: Mentor

    Oops. You're right. A and B are ruled out. E has far too many zeros. The easy way to distinguishing between C and D is to work logarithmically: 1 cm = 10E3 microns = 100E6 angstroms. On the other hand, getting down to two answers (C or D) without thinking is good all by itself.
  8. Jan 2, 2007 #7
    OK, set them equal to each other.

    10,000 microns = 100,000,000 angstrom units

    Solve for 1 micron (you can even make microns m and angstrom units a to reduce any chance of confusion and then solve for m). You can make them equal to each other like that because both have the same value: 1 cent. Ignore the incorrect posts please.

    All you have to do is cross out the zeros from dividing them and count the ones left. You can do this in your head with ease.
    Last edited: Jan 2, 2007
  9. Jan 2, 2007 #8
    Alright, I get it now. Thanks to all of you! :smile:
  10. Jan 2, 2007 #9
    By the way, how should I write down the big huge numbers when taking a test of any kind?? Should I write like that guy: 10E3=10E7 or 1x10^4=1x10^8or what?? Or should I just write out the entire number because that will make it easier to cross zeros out. Keep in mind that calculators are permitted on this test. Which will be faster and will not confused you in any way? Advice please? Thanks!
  11. Jan 2, 2007 #10


    User Avatar
    Staff Emeritus
    Science Advisor

    Whatever's easiest for you. Personally, I'd write* 104microns=108 angstrom, but if you prefer you can write out the whole number. However, I've never seen the 10E03 notation used when writing numbers, only on computers and calculators.

    *Edit: OF course, when using different numbers we would write, say, 2.5x104, and so it may be a good idea to keep the 1x104, like you've done above, to avoid confusion when learning the system. However, it is completely upto you.
    Last edited: Jan 2, 2007
  12. Jan 2, 2007 #11
    Thanks a lot cristo! your advice really helps a lot!!!:smile:
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