17- If x<0, is y>0?
10 x/y <0
2) 7-x>0
Why is A? I am thinking what if x=-3 and y=-4, still x/y ,0 BUT y <0
but if x=-3 and y=4 , y>0, I am confused...
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18- If x,y,z are positive integers, is x-y odd?
1) x=Z^2
2) y=(z-1)^2
Answer is C
Two more form internet #17, 18, section 14
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If x=-3 and y=-4, x/y is positive. Basically for x/y to be < 0, eitherisisalaska wrote:17- If x<0, is y>0?
10 x/y <0
2) 7-x>0
Why is A? I am thinking what if x=-3 and y=-4, still x/y ,0 BUT y <0
but if x=-3 and y=4 , y>0, I am confused...
x < 0 or y < 0 but not both. So, if we know that x < 0, then y has
to be positive.
1 - insufficient. Don't know yisisalaska wrote:
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18- If x,y,z are positive integers, is x-y odd?
1) x=Z^2
2) y=(z-1)^2
Answer is C
2- insufficient. Don't know x
Combining 1 and 2, z or z-1 has to be even.
If z is even, x is even and y is odd and x-y is always odd
If z is odd, x is odd and y is even and so x-y is again odd
So C
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17- If x<0, is y>0?
10 x/y <0
2) 7-x>0
Substitute values to find the answer. x<0. thus x is negative
Thus for x/y to be less 0 y would have to be positive else the x/y won't be less than 0. hence A itself is sufficient
Take the second statement
7-x > 0
This doesnt tell us anything about the variable y. Hence 2 alone is insufficient.
Thus it is choice A for question 17
10 x/y <0
2) 7-x>0
Substitute values to find the answer. x<0. thus x is negative
Thus for x/y to be less 0 y would have to be positive else the x/y won't be less than 0. hence A itself is sufficient
Take the second statement
7-x > 0
This doesnt tell us anything about the variable y. Hence 2 alone is insufficient.
Thus it is choice A for question 17
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If x,y,z are positive integers, is x-y odd?
1) x=Z^2
2) y=(z-1)^2
Statement 1 just tells us that x is the square of z. It doesn't mention anything about y. Moreover x can be odd ( example 3^2 = 9 ) or even (4 ^ 2 = 8). Thus Statement 1 alone is insufficient
Statement 2 says that y is the square of a number 1 less than z. Again z can be even or odd and thus the square of z - 1 can be odd or even respectively. Moreover it doesn't say anything about x which can be even or odd. Hence 2 alone is insufficient
Now combine the 2
Let's take z = 6 (an even number)
x = 6^2 = 36
y = (6-1)^2 = 25
36 - 25 = 11 (odd)
Lets take a case where z is odd (11)
x = 11^2 = 121
y = 10^2 = 100
121 - 100 = 21 (odd)
Hence both statements together are sufficient but neither statement alone will suffice. it's C
1) x=Z^2
2) y=(z-1)^2
Statement 1 just tells us that x is the square of z. It doesn't mention anything about y. Moreover x can be odd ( example 3^2 = 9 ) or even (4 ^ 2 = 8). Thus Statement 1 alone is insufficient
Statement 2 says that y is the square of a number 1 less than z. Again z can be even or odd and thus the square of z - 1 can be odd or even respectively. Moreover it doesn't say anything about x which can be even or odd. Hence 2 alone is insufficient
Now combine the 2
Let's take z = 6 (an even number)
x = 6^2 = 36
y = (6-1)^2 = 25
36 - 25 = 11 (odd)
Lets take a case where z is odd (11)
x = 11^2 = 121
y = 10^2 = 100
121 - 100 = 21 (odd)
Hence both statements together are sufficient but neither statement alone will suffice. it's C