Is x < 10 < y?

(1) x < y and xy = 100. If x=-20 and y=-5, then the answer is NO but if x=5 and y=20, then the answer is YES. Not sufficient.
Notice that from xy = 100 we can deduce that x and y have the same sign.

(2) x^2 < 100 < y^2 --> -10 < x < 10 and |y|>10. So, y can be more than 10 as well as less than -10. Not sufficient.

(1)+(2) Since x < y, then y < -10 is not possible, thus y > 10. So, we have that x < 10 < y. Sufficient.

Answer: C.

Hope it's clear.
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This question, from first glance, is asking the positivity or negativity of X and Y.

(1) alone is not sufficient, take x=-20, y=-5, it works; take x=5,y=20, also works. Therefore, not sufficient.
(2) alone is not sufficient neither, take x=-5, y=-20, it works; take x=5. y=20, it also works. multiple suitable cases means its not sufficient.

Combine (1) and (2) together, X <Y and XY=100 AND X^2 <100 < Y^2. This confirms that X and Y must be >0, while X must be smaller than 10 and Y is bigger than 10. Which means yes its sufficient to determine the statement (The statement is true, but we don't really need that, we just want to know if the info given is enough to DETERMINE the statement)

So C, both statements together are sufficient, but neither statement alone is sufficient.

(1) x < y and xy = 100
Both x and y could be negative.....x=-20 and y=-5......answer is NO
x=5 and y=20....answer is yes
Insufficient

(2) x^2 < 100 < y^2
-10<x<10 and y<-10 or y>10
x could be -5 or 5, while y can be 20 or -20
x=-5 and y=-20.....No
x=5 and y=20.....Yes
Insufficient


Combined
If -10<x<10, and y<-10 or y>10, then x<y only when y>10.
If y>10 and xy =100, x has to be less than 10..
Thus x<10<y
Sufficient