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Quote:



On the number line above, is the product of w, x, y, and z negative?

(1) z is positive.
(2) The product of w and x is positive

niks18 gmatbusters Bunuel VeritasPrepKarishma amanvermagmat

Please validate below approach:
Clearly statements when individually taken are insufficient.

When together:
Product of w and x is positive, implies either both w and x are positive or
both are negative. Now since y lies between x and z, it can take a positive or
negative value. Hence irrespective of z being positive, we can still have final product
as positive or negative.
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On the number line above, is the product of w, x, y, and z negative?

(1) z is positive.
it gives no info about the nature of sign of w, x, y . hence insufficient.

(2) The product of w and x is positive
it means either :
i)both w & x are positive : now y and z should also be positive, since they are on right side of w & x. hence product is positive.

ii)or both w & x are negative.: here there are 3 cases,
a) w, x, y, z = negative. product = positive
b) w, x, y = negative, z = positive. product = negative.
c) w, x= negative, y, z = positive. product = positive.

Hence insufficient.

No even after combining St 1 & 2 , we get
w, x, y = negative, z = positive. product = negative.
OR, w, x= negative, y, z = positive. product = positive.

so it is still INSUFFICIENT.

Answer = E


adkikani
Quote:



On the number line above, is the product of w, x, y, and z negative?

(1) z is positive.
it gives no info about the nature of sign of w, x, y . hence insufficient.
(2) The product of w and x is positive



Please validate below approach:
Clearly statements when individually taken are insufficient.

When together:
Product of w and x is positive, implies either both w and x are positive or
both are negative. Now since y lies between x and z, it can take a positive or
negative value. Hence irrespective of z being positive, we can still have final product
as positive or negative.
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adkikani
Quote:



On the number line above, is the product of w, x, y, and z negative?

(1) z is positive.
(2) The product of w and x is positive

niks18 gmatbusters Bunuel VeritasPrepKarishma amanvermagmat

Please validate below approach:
Clearly statements when individually taken are insufficient.

When together:
Product of w and x is positive, implies either both w and x are positive or
both are negative. Now since y lies between x and z, it can take a positive or
negative value. Hence irrespective of z being positive, we can still have final product
as positive or negative.

Yes your logic is correct.
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Your Query :
"When together:
Product of w and x is positive, implies either both w and x are positive or both are negative. Now since y lies between x and z, it can take a positive or negative value. Hence irrespective of z being positive, we can still have final product as positive or negative."


If Z is negative, We can conclude that w,x,y,z all are negative, or the product WXYZ is positive.

So your understanding, irrespective of z being positive, we can still have final product
as positive or negative
, doesn't seem right.

VeritasPrepKarishma, Please correct me.

adkikani
Quote:



On the number line above, is the product of w, x, y, and z negative?

(1) z is positive.
(2) The product of w and x is positive



Please validate below approach:
Clearly statements when individually taken are insufficient.

When together:
Product of w and x is positive, implies either both w and x are positive or
both are negative. Now since y lies between x and z, it can take a positive or
negative value. Hence irrespective of z being positive, we can still have final product
as positive or negative.
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Hi everyone,

Here is the approach i took to solve.

wxyz = Negative (-) --> Sign of each number or relative position of number with respect to zero required to know is product is negative

(1) - insuff. no info about w,x,y
(2) - insuff. no info about y,z

(1) and (2) -

W .......... X........ Y.................... ......Z
(-) ......... (-)........no info....................(+) --> things change to either positive or negative based on Y's sign
OR
(+) ........(+)........no info....................(+) ---> things change to either positive or negative based on Y's sign
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