JMEG91

Took me less than a minute to solve, yet less than 40% of the QOTDers got it wrong.

Link to the screenshot:

http://i584.photobucket.com/albums/s...T/Picture2.png

rspence

Maybe a mid-level question. It is very easy once you expand (x+y)^2. Then you realize xy = 0, and (x-y)^2 = x^2 + y^2.

xxeliza321xx

Yea. I was about to say like a 3 outta 5, 5 being hardest.

DrSteve

You can never know the level of difficulty for certain since it is determined by the experimental section of the SAT. I would actually put this one at Level 4 if I had to guess.

SATQuantum

As of now, only 33% got it right, but one has to remember that the 200,000 students that answered this question are probably the one who are motivated and are taking the SAT seriously. This means the percentile of this question for the overall SAT student population is probably less than 10%. That would put this question at Level 5 in my opinion.

I recall a question in the Old SAT red book that was similar to this:
If x^2+y^2 = 2xy, then x must be equal to:
A) -2y
B) -y
C) 0
D) y
E) 2y

I am writing the choices based on memory. That question I believe was a 4 or 5.

rspence

@SATQuantum, strange...if everyone guessed, roughly 20% would get it right. Based on the difficulty of the solution, I'd still say it's around a mid-level question (maybe level 3 or 4).

Same with the question you just posted. The equation is equivalent to (x-y)^2 = 0 --> x = y D).

xiggi

Assuming the guesses are distributed randomly and ... evenly.

As far as the level of the OP question, it should be a 4 or 5 depending where the writers decide to stick it.

I do not think that questions with multiple choices such I or I and III go below 4. But things might have changed lately.

True, but for most in SAT-landia expanding (x+y)^2 is either a forgotten or a difficult subject. Not difficult to master in the typical "short-attention-required" homework problem, but difficult to know when to apply on a SAT test.

Every SAT problem becomes very easy ... when you know HOW to solve it.

rspence

That's why I said "roughly" 20%.

Yeah, the only tricky part of this question is realizing that xy = 0 does not imply x = 0. The rest is simple...due to the fact that there are three statements you have to answer, I would probably place this at level 4, but it's definitely not level 5.

As to expanding (x+y)^2, I can't say much...other than, the US needs to improve its algebra skills.