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Math Help - GRE age word problem.

  1. #1
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    GRE age word problem.

    This is from Barron's GRE prep guide.


    If 1/2x years ago Adam was 12, and 1/2x years from now he will be 2x years old, how old will he be 3x years from now?


    The solution is:

    Since 1/2x years ago, Adam was 12, he is now 12 + 1/2x. So 1/2x years from now, he will be 12 + 1/2x +1/2x = 12 + x. But, we are told that at that time he will be 2x years old. So, 12 + x = 2x -----> x = 12. Thus, he is now 12 + 6 = 18, and 3x or 36 years from now he will be 18 + 36 = 54.

    I highlighted the 6 in the solution above as I don't know where that comes from. Can anyone help explain the solution a bit further?
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  2. #2
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    Quote Originally Posted by HKarl View Post
    This is from Barron's GRE prep guide.


    If 1/2x years ago Adam was 12, and 1/2x years from now he will be 2x years old, how old will he be 3x years from now?


    The solution is:

    Since 1/2x years ago, Adam was 12, he is now 12 + 1/2x. So 1/2x years from now, he will be 12 + 1/2x +1/2x = 12 + x. But, we are told that at that time he will be 2x years old. So, 12 + x = 2x -----> x = 12. Thus, he is now 12 + 6 = 18, and 3x or 36 years from now he will be 18 + 36 = 54.

    I highlighted the 6 in the solution above as I don't know where that comes from. Can anyone help explain the solution a bit further?
    You see where the x=12 comes from?
    And that he is now 12 + 1/2 x?
    All it's saying here is that at the moment he is 12 + 1/2 x = 12 + 1/2 * 12 = 12 + 6 =18.
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  3. #3
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    Quote Originally Posted by Unenlightened View Post
    You see where the x=12 comes from?
    Yes

    And that he is now 12 + 1/2 x?
    Yes

    All it's saying here is that at the moment he is 12 + 1/2 x = 12 + 1/2 * 12 = 12 + 6 =18.
    Edit: Yes, I see it now.

    Thanks.
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