Data Sufficiency

Material A costs $3 per kilogram, and Material B
costs $5 per kilogram. If 10 kilograms of Material K
consists of x kilograms of Material A and y kilograms
of Material B, is x > y ?
(1) y > 4
(2) The cost of the 10 kilograms of Material K is
less than $40.

I didnt understand the explanation given in the OG. Help!

Material A costs $3 per kilogram, and Material B
costs $5 per kilogram. If 10 kilograms of Material K
consists of x kilograms of Material A and y kilograms
of Material B, is x > y ?
(1) y > 4
(2) The cost of the 10 kilograms of Material K is
less than $40.

Hi Aishwarya,

Usually people get confused in understanding the second Statement which gives
3x+5y < 40

If we consider
3x+5y = 40

If you try to find it's number of solutions then you get it only for
x = y = 5

Therefore for 3x+4y to be less than 40, x must be greater than y because 3x has more impact on total cost which is bringing it lower than $40

Which explains that answer to the question "Is x>y?" will be "YES"

Hence sufficient therefore correct [spoiler]option B[/spoiler]

Thanks a ton! The written method was very helpful.

Thank you Aishwarya... This is how I teach online...

Material A costs $3 per kilogram, and material B costs $5 per kilogram. If 10 kilograms
of material K consists of x kilograms of material A and y kilograms of material B, is x > y?
(1) y > 4
(2) The cost of the 10 kilograms of material K is less than $40.

Since 10 kilograms are purchased, x+y = 10.

Statement 1: y>4
It's possible that y=5 and x=5, in which case x=y.
It's possible that y=4.5 and x=5.5, in which case x>y.
INSUFFICIENT.

Statement 2: The cost of the 10 kilograms of material K is less than $40.
If 10 kilograms are purchased at a total cost of $40, the average cost per kilogram = 40/10 = $4.
Since the total cost here is actually LESS than $40, the average cost per kilogram is less than $4 -- LESS THAN HALFWAY between x ($3) and y ($5).
For the average cost to be LESS THAN HALFWAY between x and y, more of x must be purchased, implying that x>y.
SUFFICIENT.

The correct answer is B.

Hi
IMO the answer is B
i also used the method
3x+4y=40 and started with x=4 and y=6

thanks and regards