DS Inequalities from GMAT Prep 2

[divya084]

If x-y>10, is x-y>x+y?
1) x = 8
2) y = -20

OA : D

I marked A.
Statement 1: if x = 8 and x-y>10, that means y is negative. therefore, 10> 8 + (a negative number). SUFFICIENT
Statement 2: if y = -20, x + 20 >10, x > - 10.
Assuming x to be a negative integer, say -9, 10 > - 9 - 20 , 10>-29.
Assuming x to be a positive integer, say 50, 10 > 50 -20, 10>30. Which is not correct. INSUFFICIENT.

Please tell me what is wrong wtih my reasoning above.

[nitin_prakash_khanna]

Given x-y>10

and the Q is asking x-y > x+y
re phrase 0>2y (you can subtract x from both sides without worrying about inequality sign)

is y <0?

1. St1 x= 8
8-y>10
or y<-2
so y<0 Suffcient

2. St 2 y=-20
so y<0
Sufficient

Hence Ans is D.

[divya084]

Thanks!

I'm really bad at inequality questions. Make the maximum errors there :( I guess my approach to doing them isn't the best.

[RonPurewal]

nicely done.

[himanshu_chauhan]

i want to ask that it is not given in question that x and y are +ve integer , then why din't we considered positive/Negative scenorios??

[tim]

because we can answer the question without having to worry about positives and negatives. you should keep them in mind, but it is not 100% essential that both positives and negatives be used in every question..