x and y

[ketkoag]

If x and y are positive, is 3x > 7y?
(1) x > y + 4
(2) -5x < -14y

My ans : B OA: D
my explanation. by statement 1 let y=5, x = 10
then 3x = 30,
7y = 35
therefore : 3x<7y

now let y = 20, x = 100 then 3x = 300
and 7y = 140
therefore 3x>7y
hence not sufficient.

by statement 1 it clearly shows that 3x>7y
so IMO B

[mike22629]

You are right, the OA is wrong

Just remember, whenever comparing ratios to see which one is greater, if an equation includes adding or subtracting a constant, it is generally insufficient, unless the question has some type of stipulation that makes it possible.

[schumi_gmat]

IMO D.

B is sufficint as you have done it

A. x>y+4

plugin values -

x= 4, y+4=3; y=-1
therefore, 3x>7y

x=-3, y+4=-4; y=-8
3x>7y

x=0, y+4=-1; y=-1
3x>7y

x=1/2, y+4=1/3; y=-11/12
3x>7y

x=-1/3; y+4=-1/2; y=-9/2
3x>7y

Hence SUFF

Ans D.

Ketkoag,
I saw your solution and it seems correct as well. I am really confused with this question.
What is the source of the question?

[typhoonguywlblwu]

IMO B as well as

-5x < -14y ,multiplying it by -1 and reversing the sign,
5x > 14y .....multiplying it by 3
15x > 42y

we need to find if 3x>7y ,multiplying it by 5
15x > 35y

clearly b is suff.

On stmt a,taking the discussion a bit further from schumi's solution,
if x=100 , y could be 95

clearly,3x100=300 is not greater than 95X7=665

but if x=5, y could be 1

subsituting values for x & y 15 > 7 hence stmt is insufficient


Maybe we need an expert's opinion.what you think guys?

[ketkoag]

IMO D.

B is sufficint as you have done it

A. x>y+4

plugin values -

x= 4, y+4=3; y=-1
therefore, 3x>7y

x=-3, y+4=-4; y=-8
3x>7y

x=0, y+4=-1; y=-1
3x>7y

x=1/2, y+4=1/3; y=-11/12
3x>7y

x=-1/3; y+4=-1/2; y=-9/2
3x>7y

Hence SUFF

Ans D.

Ketkoag,
I saw your solution and it seems correct as well. I am really confused with this question.
What is the source of the question?

x and y are positive..