Sponsored Ad:
Results 1 to 8 of 8

Thread: Need help on this one.

  1. #1
    Trying to make mom and pop proud
    Join Date
    Oct 2004
    Location
    new york
    Posts
    10
    Rep Power
    16


    Good post? Yes | No

    Need help on this one.

    Sponsored Ad:
    If (x^2) + 5y=49, is y an integer?
    (1) 1 < x < 4
    (2) (x^2) is an integer

    I say combined together, they are sufficient, ....

    ....since the first statement, if x were either 2 or 3, y would be an integer, but we're not told that x is an integer so the fact that (x^2) could be fraction is possible. so INSUFFICIENT

    ... but the second statement tells us that x is an integer. alone, that's INSUFFICIENT..

    .. but combined, we're basically told that x can either be 2 or 3 which makes 49-(x^2) a multiple of 5. So I chose C.

    Please tell me why this way of solving the question is wrong since the answer is saying that it should be E.

  2. #2
    Eager! maria1_03's Avatar
    Join Date
    Oct 2004
    Location
    Bucharest
    Posts
    65
    Rep Power
    16


    Good post? Yes | No

    Re: Need help on this one.

    For example if x = 3/2 than 5y = 46, so y isn’t an integer…. That’s why the answer is E…

  3. #3
    Trying to make mom and pop proud
    Join Date
    Oct 2004
    Location
    new york
    Posts
    10
    Rep Power
    16


    Good post? Yes | No

    Re: Need help on this one.

    3/2 as in the fraction 3 over 2? But statement 2 satisfies the necessity for (x^2) of being an integer and not a fraction, no?

  4. #4
    Eager! maria1_03's Avatar
    Join Date
    Oct 2004
    Location
    Bucharest
    Posts
    65
    Rep Power
    16


    Good post? Yes | No

    Re: Need help on this one.

    Quote Originally Posted by ak78
    3/2 as in the fraction 3 over 2? But statement 2 satisfies the necessity for (x^2) of being an integer and not a fraction, no?

    yes.. I was thinking of 1.5... it's between 1 and 4 and 1.5 * 2 = 3 which is an integer... we know that x*2 is an integer and not necessary x is an integer... hope u understand what I want to say

  5. #5
    Trying to make mom and pop proud
    Join Date
    Oct 2004
    Location
    new york
    Posts
    10
    Rep Power
    16


    Good post? Yes | No

    Re: Need help on this one.

    sorry --- when i typed x^2, i was using the format i usually used in my TI-82 or TI-85 calculator, i mean x squared.

    sorry for the confusion. now do you see why I might be confused with the answer though?

  6. #6
    An Urch Guru Pundit Swami Sage gmat168's Avatar
    Join Date
    Apr 2004
    Posts
    1,255
    Rep Power
    22


    Good post? Yes | No

    Re: Need help on this one.

    OK, statement 1: x can be an integer, x can be afraction. really doesn't help.

    Statement 2: Alone, this is insufficient, as x can equal sqrt2, sqrt3, 2, etc.

    Combined: Still insufficient. If x were 2, yes, then y is an integer. If x = sqrt2, then y is not an integer.

  7. #7
    Eager! Salila's Avatar
    Join Date
    Nov 2004
    Location
    India
    Posts
    37
    Rep Power
    16


    Good post? Yes | No

    Re: Need help on this one.

    Hi ak,

    If (x^2) + 5y=49, is y an integer?
    (1) 1 < x < 4
    (2) (x^2) is an integer

    Here's my explanation :

    Q: x^2 + 5y=49
    5y = 7^2 - x^2 => (7-x) (7+x)
    y = (7-x) (7+x)/5

    (1) 1 < x < 4 ,so x can be anything from 1.5, 2,2.5 ...so on upto 4
    As you already know ,y is an integer when x is an integer 2 or 3 ,otherwise y is a fraction. So the data is insufficient.

    (2) (x^2) is an integer :

    Meaning x is sqrt "n" where n can be a number from 1,2,3,4....n. The answer is yes and no , that makes it insufficient too.

    Combining statement (1) and (2) ,x is a sqrt and lies between 1 and 4. We are left with options like sqrt2 ,sqrt3 ,sqrt 4 ,sqrt 5...so on.
    We know y = (7+sqrt2)(7-Sqrt2)/5 is not an integer.
    We know y = (7+2)(7-2)/5 is an integer.

    So the data is insufficient. There !!
    Last edited by Salila; 11-15-2004 at 10:13 AM. Reason: smiley

  8. #8
    Trying to make mom and pop proud
    Join Date
    Oct 2004
    Location
    new york
    Posts
    10
    Rep Power
    16


    Good post? Yes | No

    Re: Need help on this one.

    aHa.

    geez. didn't think of sqrt2, sqrt3. thanks! i wish the frikkin test explanation itself would have said that.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •