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Homework Help: HelpBasic math

  1. Jan 27, 2006 #1
    I am new to this type of math. I need help.............



    Can any one point to me to a good web site where I can learn about rounding and stuff.


    Here is another one I am struggling with. I looked in the internet could not find one that really explains it well

    How to estimated 3.9 * 7.4 using front end rounding?

    How to estimated 33.294/6.2, again using front end rounding?

    Arrange in assending order the following: 0.321,0.302,8/25

    This one look straight forward as 8/25 = 0.32 --> 0.302, 8/25, 0.321
    But if I am mindful about sig figures 8/25 = 0.3 and my assending order becomes, 8/25,0.302, 0.321.


    Any help or hint is much appreciated.

    Thanks,

    gamma.
     
  2. jcsd
  3. Jan 28, 2006 #2

    HallsofIvy

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    Science Advisor

    I doubt you need a whole web site for that! "Front end rounding" just means round to the nearest one digit number. Since 3.9 is closer to 4 than to 3 (since 9> 5) it rounds to 4. 7.4 rounds to 7. What is 4*7?

    Same idea. 33.294 rounds to 30, 6.2 to 6. What is 30/6?

    Good! That's exactly right!

    No. "significant figures" is only used with approximate figures (like measurements). The integers in a fraction are never approximate. You could think of 8/25 as 8.0000/25.0000 is you like. The correct order is
    0.302, 8/25, 0.321 as you gave before.
     
  4. Jan 28, 2006 #3
    nicely explained.... thank you HallsofIvy. These stuff were not in our curriculum during my school days (not usa) and that is hunting me now.

    Thanks,

    Gamma.
     
  5. Jan 29, 2006 #4

    t!m

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    Mm, I'd be careful with front-end rounding. There's really no 'standard' way to do it, but it certainly is not your basic rules for rounding, i.e. >5 rounds up. The most common, and simple way, I remember being taught front-end rounding was to simply use the first digit of each number, hence front-end.

    For 3.9*7.4, I would bet that this is meant to be 3*7, using front-end. It certainly isn't an accurate approximation, but it's a fast one, and one that I remember being taught.

    There are all kinds of 'correction' techniques, but that would vary by the curriculum.
     
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