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by papgust » Sun Jan 03, 2010 3:11 am
For your 1st qn, statement II is alone sufficient. Check the attachment.
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by papgust » Sun Jan 03, 2010 3:14 am
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
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by papgust » Sun Jan 03, 2010 3:16 am
4th qn., root(x^2)/x = (x^2)^1/2 / x = x/x = 1
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by thephoenix » Sun Jan 03, 2010 4:00 am
papgust wrote:4th qn., root(x^2)/x = (x^2)^1/2 / x = x/x = 1
imo its E

sqrt(x^2)=+-x=lxl

hence rut(x^2)/x=lxl/x
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by thephoenix » Sun Jan 03, 2010 4:11 am
papgust 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)
B is insuff as x/y will be > 1 if x > y>0 or if x<y<0

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
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by sadullaevd » Mon Jan 04, 2010 4:54 am
thephoenix wrote:
papgust wrote:4th qn., root(x^2)/x = (x^2)^1/2 / x = x/x = 1
imo its E

sqrt(x^2)=+-x=lxl

hence rut(x^2)/x=lxl/x
exactly, imo E.

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.
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