Data Sufficiency

Can someone please help me understand this?

A

yes the answer is A but can you explain pls

Stmt I )

1/k-1 > 0

Mutiply both sides of inequality by (k-1)^2

k-1>0
k>1

So 1/k > 0 SUFF

Stmt II

1/k+1 > 0

Mutiply both sides of inequality by (k+1)^2

k+1>0
k>-1

We dont knoe if 1/k > 0( If k is -ve fraction then NO If k is positive fraction/integer then yes) INSUFF

A)

Basically the question boils down to Is k positive.

If yes 1/k > 0
If no then 1/k<0

Hope this helps!

the question asks if k is +ve

from one

K-1>0 thus k>1................suf

From 2

k+1>1.......k>-1 ( can be +ve or -ve)........insuff

A

imo A - but with substitution

statement 1 says: 1/(k-1)>0

as we know k cannot be 0,1 or -1

with statement 1 it is also true that k cannot be a negative number

for example k = -2

then,

1/(k-1)>0 becomes 1/(-2-1) or 1/(-3)>0 or -1/3>0 (which cannot happen)

so K always has to be positive and if k is positive then 1/(+ve k) is always greater than 0

NOW MOVING ON.....

Statement 2

1/(k+1)>0

if K is positive we are good as 1/(+ve K) will always be greater than 0.

but if K is -0.5

then 1/(-0.5+1)>0
or 1/0.5 > 0
or 2>0

statement 2 holds true but it makes 1/k = 1/(-0.5) = -2 which is less than 0
so statement 2 is insufficient

Remember: If the question does not mention the word integer, test for fractions as well.

cramya wrote:Stmt I )

1/k-1 > 0

Mutiply both sides of inequality by (k-1)^2

k-1>0
k>1

A)

Cramya,

How can you multiply both sides of the inequality by (K-1)^2? Since you don't know whether K is positive or negative, you wouldn't know which way the inequality sign would flip. Right?

Stockmoose16 wrote:

cramya wrote:Stmt I )

1/k-1 > 0

Mutiply both sides of inequality by (k-1)^2

k-1>0
k>1

A)

Cramya,

How can you multiply both sides of the inequality by (K-1)^2? Since you don't know whether K is positive or negative, you wouldn't know which way the inequality sign would flip. Right?

A square is always positive tough 8)

logitech wrote:

Stockmoose16 wrote:

cramya wrote:Stmt I )

1/k-1 > 0

Mutiply both sides of inequality by (k-1)^2

k-1>0
k>1

A)

Cramya,

How can you multiply both sides of the inequality by (K-1)^2? Since you don't know whether K is positive or negative, you wouldn't know which way the inequality sign would flip. Right?

A square is always positive tough 8)

So you wouldn't be able to simply multiply by (k-1) then? Only (k-1)^2?

Stockmoose16 wrote:

logitech wrote:

Stockmoose16 wrote:

cramya wrote:Stmt I )

1/k-1 > 0

Mutiply both sides of inequality by (k-1)^2

k-1>0
k>1

A)

Cramya,

How can you multiply both sides of the inequality by (K-1)^2? Since you don't know whether K is positive or negative, you wouldn't know which way the inequality sign would flip. Right?

A square is always positive tough 8)

So you wouldn't be able to simply multiply by (k-1) then? Only (k-1)^2?

in this case you can use the SQUARE - because it is always + , but never multiply or divide an inequality with something without knowing its SIGN