Source Grockit: DS: Inequallity

[polter]

If m ≠ -n, is (m-n)/(m+n)> 1?

(1) n < 0

(2) m > 0

[spoiler]E[/spoiler]

I think the correct answer should be different.

[shantanu86]

If m ≠ -n, is (m-n)/(m+n)> 1?

(1) n < 0

(2) m > 0

E

I think the correct answer should be different.

Hi polter,

Pls go th. https://www.beatthegmat.com/fast-way-to- ... tml#467098

Regards,
Shantanu

[spartacus1412]

the question says m +n =0 (given m!= -n)
to find if (m-n)/(m+n)> 1?

this can be reduced to (m-n)/(m+n) -1 >0
i.e. -2n/(m+n)>0


option1: n<0
we cannot say anything about the sign of m+n. hence, above expression can be + as well as -
hence, insufficient.


option1: m>0
we cannot say anything about the sign of above expression. hence, above expression can be + as well as -
hence, insufficient.


combine both : n<0 and m>0
the above expression wil be less than zero only if abs(n)> abs(m), which is not given.


hence, both together are insufficient.
Answer, E

Hope it Helps

[polter]

Hi shantanu86/ spartacus1412, thank you for your suggestions.

My confusion was with this: can this expression not be reduced as
(m-n)/(m+n)> 1
=> (m-n)> (m+n)
=> -n > n
=> 0 > 2n
=> 0 > n

Since (1) clearly defines this. Hence A

[Stuart@KaplanGMAT]

Hi shantanu86/ spartacus1412, thank you for your suggestions.

My confusion was with this: can this expression not be reduced as
(m-n)/(m+n)> 1
=> (m-n)> (m+n)
=> -n > n
=> 0 > 2n
=> 0 > n

Since (1) clearly defines this. Hence A

Hi!

Whenever you see inequalities and variables, alarm bells should go off in your head and your internal warning system should be shouting "DANGER DANGER DANGER!!!"

Remember this key difference between equations and inequalities:

When you multiply or divide both sides of an inequality by a negative number, you flip the inequality.

With that rule in mind, here's the mistake you made: you divided both sides by (m+n) without knowing whether that term was positive or negative.