Friday, October 2, 2009

Problem 54 - GMAT Algebra


4 comments:

  1. (2) 4 > w > z > 0, so z < 4, sufficient. We are left with B and D

    (1) 1/w < 1/x < 1/y < 1/z (from the question stem)
    1/w + 1/x + 1/y + 1/z < 4/z
    1 < 4/z
    z < 4

    So, (D) is the answer

    ReplyDelete
  2. Yep, answer is D. Statement 2 is the easy one, cross multiply ant that's it.

    The other way of looking at 1 is to see that if all your guys are equal to, say, 4 each, then they add up to one, but we are told that z is less than all the other guys, so the other fractions will be less than 1/z, so to allow the other fractions to be more than 1/4, z must be less than 4.

    ReplyDelete
  3. I keep getting B as the correct answer.

    1/w > 1/4, so w < 4.

    from original we know w > z > 0, so 3.999 > z > 0, thus Z must be less than 4. What am I missing? Thanks! -Mike

    ReplyDelete
  4. Mike,
    Per question:
    w > x > y > z , take the reciprocal(reverse inequality )
    1/w < 1/x < 1/y < 1/z
    Add all:
    1/w + 1/x + 1/y + 1/z now since 1/z is the largest of the 4 terms the sum has to be less than 4/z
    or 1/w + 1/x + 1/y + 1/z < 4/z
    But Lft side =1 per 1
    1 < 4/z
    z < 4
    2: is straight forward, just cross multiply
    w < 4 and z < w , hence z < 4.
    D

    ReplyDelete