On Page 222 they have thus DS question
Is it true that X < Y?
1 5x < 5y
2 zx < zy
I thought the answer should be D. They say it is A.
Explaination is that in second statement Z could be +ve or -ve.
I chose D because we are already given zx < zy. Isn't it true that we have to assume that statement 2 is true.
Similarly on page 223
the question is
If X and Y are integers, does x = y?
1) xy = y2 (2 here is square)
2) x2 = y2 (2 here is square)
I thought the answer should be again D but the book says it is C.
few princeton review DS questions from 2nd ed math workout
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[quote="coachy"]On Page 222 they have thus DS question
Is it true that X < Y?
1 5x < 5y
2 zx < zy
I thought the answer should be D. They say it is A.
Explaination is that in second statement Z could be +ve or -ve.
I chose D because we are already given zx < zy. Isn't it true that we have to assume that statement 2 is true.
[/quote]
[size=18]x < y holds true from 5x < 5y for all values of x and y. So, (1) is
sufficient.
zx < zy does not necessarily mean x < y, as we don't know whether
z is positive or negative. So, (2) is insufficient.
Hence A.
[/size]
[quote="coachy"]
Similarly on page 223
the question is
If X and Y are integers, does x = y?
1) xy = y2 (2 here is square)
2) x2 = y2 (2 here is square)
I thought the answer should be again D but the book says it is C.[/quote]
Can you please explain why this should be D ?
(1) is sufficient as you can safely cancel out y from both sides
leading to x = y
I'd say (2) is insufficient as x^2 = y^2 can be expressed as
(x+y)(x-y)=0 which means x = y or x=-y.
Is it true that X < Y?
1 5x < 5y
2 zx < zy
I thought the answer should be D. They say it is A.
Explaination is that in second statement Z could be +ve or -ve.
I chose D because we are already given zx < zy. Isn't it true that we have to assume that statement 2 is true.
[/quote]
[size=18]x < y holds true from 5x < 5y for all values of x and y. So, (1) is
sufficient.
zx < zy does not necessarily mean x < y, as we don't know whether
z is positive or negative. So, (2) is insufficient.
Hence A.
[/size]
[quote="coachy"]
Similarly on page 223
the question is
If X and Y are integers, does x = y?
1) xy = y2 (2 here is square)
2) x2 = y2 (2 here is square)
I thought the answer should be again D but the book says it is C.[/quote]
Can you please explain why this should be D ?
(1) is sufficient as you can safely cancel out y from both sides
leading to x = y
I'd say (2) is insufficient as x^2 = y^2 can be expressed as
(x+y)(x-y)=0 which means x = y or x=-y.