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Re: Inequality Question [#permalink]
06 Jan 2014, 00:20

1

This post received KUDOS

boyanshmorhun wrote:

If all variables are positive, is (w/x) > (y/z)?

1) w = y + 50 2) x = z + 50

1) and 2) alone are INS.

(y+50)/(z+50) > y/z yz +50z > yz +50y 50y > 50z y > z

Both together are INSUFICIENT so E)

My question is, however: The first time that I worked it out, I simply did this...

If w = y + 50 , then w > y If x = z + 50 , then x > z

Divide equations by each other:

(w > y) ÷ (x > z) = (w/x) > (x/z)

Why isn't this right?

Hi

You can't divide with relational operators as all the w,x,y,z are variable and +ve. They can be equal in pairs.

consider the simple example :

y= 1 w= 1+50= 51

z = 1 x= 51

So w/x = y/z

So doing a division operation in relational operator with variable is not so good appraoch where you dont know the range of the number. _________________