GMAT PREP QUESTIONS
This topic has expert replies
-
- Senior | Next Rank: 100 Posts
- Posts: 30
- Joined: Thu Jan 22, 2009 9:34 pm
Could u please help me with my doubts
- Attachments
-
- doubts 2.doc
- (98 KiB) Downloaded 107 times
-
- doubts.doc
- (122 KiB) Downloaded 121 times
- papgust
- Community Manager
- Posts: 1537
- Joined: Mon Aug 10, 2009 6:10 pm
- Thanked: 653 times
- Followed by:252 members
3rd qn., Are x and y both positive?
A. 2(x-y) = 1
x-y = 1/2. x and y can be +ve or -ve. Try plugging in values to check this. Insufficient.
B. x/y > 1
or x > y
You don't whether x is +ve,-ve or y is +ve,-ve. Insufficient.
Combined,
you know x > y from B. To satisfy x - y = 1/2, x and y have to be +ve. You could even try out some scenarios to confirm.
Sufficient. C
A. 2(x-y) = 1
x-y = 1/2. x and y can be +ve or -ve. Try plugging in values to check this. Insufficient.
B. x/y > 1
or x > y
You don't whether x is +ve,-ve or y is +ve,-ve. Insufficient.
Combined,
you know x > y from B. To satisfy x - y = 1/2, x and y have to be +ve. You could even try out some scenarios to confirm.
Sufficient. C
- thephoenix
- Legendary Member
- Posts: 1560
- Joined: Tue Nov 17, 2009 2:38 am
- Thanked: 137 times
- Followed by:5 members
imo its Epapgust wrote:4th qn., root(x^2)/x = (x^2)^1/2 / x = x/x = 1
sqrt(x^2)=+-x=lxl
hence rut(x^2)/x=lxl/x
- thephoenix
- Legendary Member
- Posts: 1560
- Joined: Tue Nov 17, 2009 2:38 am
- Thanked: 137 times
- Followed by:5 members
B is insuff as x/y will be > 1 if x > y>0 or if x<y<0papgust wrote:3rd qn., Are x and y both positive?
B. x/y > 1
or x > y
for a variable crossmultiplication is not correct ( as the signs are not)
hence bth can be -ve or +ve
combinng
x-y=1/2
x/y>1--->x/y - 1>0---->(x-y)/y>0---->1/2y >0----> y>0----> x>0
hence bth +ve and hence C
-
- Senior | Next Rank: 100 Posts
- Posts: 81
- Joined: Wed Apr 08, 2009 3:12 pm
- Location: South Korea
- Thanked: 4 times
exactly, imo E.thephoenix wrote:imo its Epapgust wrote:4th qn., root(x^2)/x = (x^2)^1/2 / x = x/x = 1
sqrt(x^2)=+-x=lxl
hence rut(x^2)/x=lxl/x
Since we don't know whether x has positive or negative sign, example.. plug 4 and -4 then u can see that results will be different.
Stay skeptical,
Think critically,
Assume nothing.
Think critically,
Assume nothing.