If there are x men and y women in a choir, and there are z more men

Hi sabineodf,

Many Quant questions on Test Day are pattern-based, so instead of looking at a prompt and thinking "what is this?", try thinking "what does this REMIND ME of?" In that way, you'll probably be less intimidated by the structure of the questions.

The prompt is worded in a 'quirky' way, but the information isn't that complex. From the two Facts, you should recognize that we're meant to be thinking about Classic Quadratics. If you're familiar with the 3 Classic Quadratics, then the bulk of the work in this question is just about re-writing information (and not about hard-core math skills).

For example, you are expected to know that....

X^2 -2XY + Y^2 can be re-written as....

(X-Y)(X-Y) =

(X-Y)^2

If you're not familiar enough with those ideas/rules yet, then that's okay, but you DO have to have to become familiar and practice them. Algebra is a BIG category in the Quant section, so you have to make sure that you're familiar enough with the broad concepts (and can do the specific calculations when required).

GMAT assassins aren't born, they're made,
Rich

That was very helpful, thanks!

This question is just testing quadratic templates

St 1

(x-y)(x-y) =9

Since this question is basically asking for the difference between a certain amount of people the answer can't necessarily be negative so x-y =2

suff

St 2

(x +y)(x+y) =225

insuff

A

x and y ---> choir
x=z+y ----> x-y=z
1) x^2-2xy+y^2=9
(x-y)^2=9
therefore, x-y= 3
2) Insufficient because solving statement 2, we would get x+y=15 which is of no use.
This is my understanding about the question. Please correct me if I am wrong.
Thank you.

Pretty simple once we understand what the question is asking.

There are x men and y women. We are told that there are more men than women and that this difference is z.

Let's set this up as an equation: x-y=z. We'll see if those shows up in the prompts.

1) rewrite this as: (x-y)^2-9=0
(x-y)^2=9
X-y= 3 =z

Sufficient.

2) (x+y)^2= 225
X+y= 15
Z=?

Insufficient.

Answer A.

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Hi Bunuel : Since we're dealing with the physical entities, is that the sole reason why option A is correct, i.e. X-Y= +/- 3 and men cannot be negative 3, so we go with 3 as the value for Z? Had we have a case to find the value for just the variable, the answer would have been E. Is my understanding correct?