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MGMAT Found of Math Fractions | Simplify: (√3/2)-(√3/8)

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mkofron Newbie | Next Rank: 10 Posts Default Avatar
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MGMAT Found of Math Fractions | Simplify: (√3/2)-(√3/8)

Post Sat Nov 05, 2016 4:42 pm
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    Simplify: (√3/2)-(√3/8)

    Why does the answer explanation not use √8 as the common denominator? Is this illegal?


    "Treat this as a standard fraction subtraction problem: find common denominators so that you can subtract. Begin by splitting the square root symbols across the numerator and denominator."
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    melguy Master | Next Rank: 500 Posts
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    Post Sat Nov 05, 2016 6:14 pm
    In this problem you have to find the LCM like any other fraction problem.

    You would make your life difficult if you take the numerical approach. Considering we have to solve the problem in under two minutes we are supposed to find the easiest approach which would be to simply use √8 x √2 giving us √16 (i.e. 4).

    Post Sat Nov 05, 2016 8:46 pm
    Hi mkofron,

    YES - you could use root8 as the common denominator. Did you try to do so? How many math 'steps' did it take you to get to the correct answer (and when you compare that work to the work shown in this explanation, which option looked easier?)?

    GMAT assassins aren't born, they're made,
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    mkofron Newbie | Next Rank: 10 Posts Default Avatar
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    Post Sat Nov 05, 2016 9:12 pm
    I did try the root8 method but I could not manipulate the expressions to get to any of the answer choices. Neutral Which tells me I have a deficiency somewhere....I get the that root16 is quicker but I am also trying to figure out why I can't make the the root8 method work.

    Thanks,
    Matt

    Post Sun Nov 06, 2016 12:19 pm
    Hi Matt,

    Could you post a pic/screen capture of your work so that I can see where you got 'stuck?'

    GMAT assassins aren't born, they're made,
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    mkofron Newbie | Next Rank: 10 Posts Default Avatar
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    Post Sun Nov 06, 2016 2:01 pm
    Hey Rich,

    Thanks for getting back. Here is how I tried to do it.


    You can see I made a silly mistake in the denominator (sqrt 18 instead of sqrt 8) and corrected it before I took this photo. I appreciate the help.

    Regards,
    Matt

    mkofron Newbie | Next Rank: 10 Posts Default Avatar
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    Post Sun Nov 06, 2016 3:18 pm
    OK, I see what I neglected to do. I just needed to get the square root out of the denominator in my step #6. My original answer choice is equivalent to the correct answer just not as simplified.

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