My reasoning? Here's what I do on the M/C portion of the CPA exams.
When I'm stuck on a question, I look for "power words" such as: all, always, never, only. Those are mostly likely not the answer.
Then I look at the other choices and see which one is longer. Normally I'd pick the longest answer choice. If they're almost equal in length, I stick with C.
If I had to face a something like this in real life, I would google it. And guess what? BAM!! Here's the answer:
Use the difference of squares formula, a^2 - b^2 = (a + b)(a - b)
(x+y)^2 - (x-y)^2 = (x+y+x-y)(x+y-x+y) = 2x*2y = 84 xy = 21 Since x and y are given to be positive integers, only 1 and 21 or 3 and 7 will work. 22 is not one of the choices, so the answer is x+y = 10.
6 comments:
Are you freaking kidding me? Tell me when, in this life time will you ever have to do a math question like this (besides the SATs, GMAT, etc.).
If this were on my exam, I'd pick C.
My reasoning? Here's what I do on the M/C portion of the CPA exams.
When I'm stuck on a question, I look for "power words" such as: all, always, never, only. Those are mostly likely not the answer.
Then I look at the other choices and see which one is longer. Normally I'd pick the longest answer choice. If they're almost equal in length, I stick with C.
=)
Now, do you really want me to do your taxes?
I'm just baffled!
If I had to face a something like this in real life, I would google it. And guess what? BAM!! Here's the answer:
Use the difference of squares formula, a^2 - b^2 = (a + b)(a - b)
(x+y)^2 - (x-y)^2 = (x+y+x-y)(x+y-x+y) = 2x*2y = 84
xy = 21
Since x and y are given to be positive integers, only 1 and 21 or 3 and 7 will work. 22 is not one of the choices, so the answer is x+y = 10.
I found out how to do this without cheating with google:
(x+y)^2-(x-y)^2 = 84
[(x+y)(x+y)]-[(x-y)(x-y)]=84
Let's remember our friend "FOIL"
(x^2+xy+xy+y^2)-(x^2-xy-xy+y^2)=84
cancel out the like terms
the x^2 & y^2 cancels each other out, right?
that leaves you with
xy+xy+xy+xy=84
that's 4xy = 84
xy = 21
DAMN, that was too much thinking!
Aahahahah...I check the blog and suddenly have 4 comments!
This was actually one of Maggie's PSAT questions. She asked me, I had no idea, so I posted it.
I had totally forgotten about foiling! I had to consult a math guru, who basically told me what you wrote on your 4th comment.
Why would someone need to do this at a tender age of 16? I just don't get it.
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