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Crazy SAT math question

post #1 of 10
5/3/03 at 5:44pm
Thread Starter 
I took the SAT today, and there was a math problem which befuddled me to no end. I could use some help, folks.

If XY=7, and X-Y=5, then X^2*Y-X*Y^2=
a. 2
b. 12
c. 24
d. 35
e. 70

Holy moley. I do not get it.
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post #2 of 10
5/3/03 at 7:18pm
Well, that's really quite simple. I'm a little surprised that you didn't get it. As a matter of fact the answer is......(*(*(*(*HEAD EXPLODES*)*)*)*)

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post #3 of 10
5/3/03 at 7:25pm
Quote:
Koyaanisqatsi:
I took the SAT today, and there was a math problem which befuddled me to no end. I could use some help, folks.

If XY=7, and X-Y=5, then X^2*Y-X*Y^2=
a. 2
b. 12
c. 24
d. 35
e. 70

Holy moley. I do not get it.
Well, you're given that xy=7 and that x-y=5. So you can assume x=y+5, and therefore y*(y+5)=7. Multiply it out and then that gives us the equation y^2+5y-7=0, which you should be able to factor out, but for the life of me I can't figure out what it would come out to.
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post #4 of 10
5/3/03 at 7:58pm
If xy=7 and x-y=5

x^2y-xy^2= ?
x(xy)-(xy)y=
7x-7y=
7(x-y)=
7 * 5 = 35
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post #5 of 10
5/3/03 at 8:35pm
Rylander gets to leave class 5 minutes early.
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post #6 of 10
5/3/03 at 8:37pm
Please tell me that SAT math questions get more demanding than that.
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post #7 of 10
5/3/03 at 8:37pm
Well, that's why I majored in English.
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post #8 of 10
5/3/03 at 9:29pm
Thread Starter 
Quote:
Rylander:
If xy=7 and x-y=5

x^2y-xy^2= ?
x(xy)-(xy)y=
7x-7y=
7(x-y)=
7 * 5 = 35
Yeah. Um, I think I'm missing the logic in there. Why are you allowed to just stick those 7's in there.

I hate math.
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post #9 of 10
5/3/03 at 9:35pm
Because XY=7
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post #10 of 10
5/3/03 at 10:52pm
Lucky me. I never had to take the SAT. I did take the ACT twice, though.

And like DWC, my head would exploded like his if I even attempted to solve that question.
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