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.
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