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Two more form internet #17, 18, section 14

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isisalaska Community Manager Default Avatar
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Two more form internet #17, 18, section 14

Post Tue Mar 27, 2007 1:01 pm
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    17- If x<0, is y>0?
    10 x/y <0
    2) 7-x>0
    Why is A? I am thinking what if x=-3 and y=-4, still x/y ,0 BUT y <0
    but if x=-3 and y=4 , y>0, I am confused...

    _________________________________________

    18- If x,y,z are positive integers, is x-y odd?
    1) x=Z^2
    2) y=(z-1)^2

    Answer is C

    _________________
    Isis Alaska

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    jayhawk2001 Community Manager
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    Post Tue Mar 27, 2007 10:00 pm
    isisalaska wrote:
    17- If x<0, is y>0?
    10 x/y <0
    2) 7-x>0
    Why is A? I am thinking what if x=-3 and y=-4, still x/y ,0 BUT y <0
    but if x=-3 and y=4 , y>0, I am confused...

    If x=-3 and y=-4, x/y is positive. Basically for x/y to be < 0, either
    x < 0 or y < 0 but not both. So, if we know that x < 0, then y has
    to be positive.

    isisalaska wrote:
    _________________________________________

    18- If x,y,z are positive integers, is x-y odd?
    1) x=Z^2
    2) y=(z-1)^2

    Answer is C
    1 - insufficient. Don't know y
    2- insufficient. Don't know x

    Combining 1 and 2, z or z-1 has to be even.
    If z is even, x is even and y is odd and x-y is always odd
    If z is odd, x is odd and y is even and so x-y is again odd

    So C

    Cybermusings Legendary Member Default Avatar
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    Post Wed Mar 28, 2007 3:17 am
    17- If x<0, is y>0?
    10 x/y <0
    2) 7-x>0

    Substitute values to find the answer. x<0. thus x is negative

    Thus for x/y to be less 0 y would have to be positive else the x/y won't be less than 0. hence A itself is sufficient

    Take the second statement

    7-x > 0

    This doesnt tell us anything about the variable y. Hence 2 alone is insufficient.

    Thus it is choice A for question 17

    Cybermusings Legendary Member Default Avatar
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    Post Wed Mar 28, 2007 3:28 am
    If x,y,z are positive integers, is x-y odd?
    1) x=Z^2
    2) y=(z-1)^2

    Statement 1 just tells us that x is the square of z. It doesn't mention anything about y. Moreover x can be odd ( example 3^2 = 9 ) or even (4 ^ 2 = 8). Thus Statement 1 alone is insufficient

    Statement 2 says that y is the square of a number 1 less than z. Again z can be even or odd and thus the square of z - 1 can be odd or even respectively. Moreover it doesn't say anything about x which can be even or odd. Hence 2 alone is insufficient

    Now combine the 2

    Let's take z = 6 (an even number)

    x = 6^2 = 36

    y = (6-1)^2 = 25

    36 - 25 = 11 (odd)

    Lets take a case where z is odd (11)

    x = 11^2 = 121

    y = 10^2 = 100

    121 - 100 = 21 (odd)

    Hence both statements together are sufficient but neither statement alone will suffice. it's C

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