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by goyalsau » Wed Oct 20, 2010 4:12 am
HI! Guys

[spoiler]OA is this question is D,
They are making equation from the statements as
x - 6000 = 4.5 ( y - 6000 ) and then using the x = 3y

Same with II statement.
I want to know , X and Y is mileage , How can we subtract miles driven from the mileage ..

WHAT IS THE LOGIC

I am totally confused Please Help....[/spoiler]
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by shovan85 » Wed Oct 20, 2010 7:43 am
Because Mileage is literally a distance measured in miles.
So in other words car X travels the distance in miles = 3 times of the car Y travels the distance in miles
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by fskilnik@GMATH » Wed Oct 20, 2010 9:26 am
Hi guys,

Nice to be here.

Yes, I understood the question stem as Shovan did...

Let dX and dY be the distances in miles that X and Y have "run" (till now).

We know that dX = 3dY and we are asked the value of dX .

Important: please note that dX value will be DECIDED if and only if dY value will be DECIDED. (I will use that below.)

(1) dX - 6000 = 4.5 (dY - 6000) if and only if 3dY - 6000 = 4.5dY - 4.5 times 6000

Note that this last equation is FIRST DEGREE (on variable dY), therefore there is a UNIQUE possible value for dY. Nothing more is needed to be done, because the value of dY is DECIDED and by the "Important" above the same can be said of dX.


(2) Exactly the same reasoning. Do it!


Conclusion: you just have to see that 3dY and 4.5Y does not cancel each other out... I mean, we have a FIRST degree equation if you can put the equation in the form ax+b = 0 where a is not null... after checking that, and in our case a equals 3-4.5 (or 4.5-3), we are safe to say that the statement is sufficient to answer the question asked.

Question: what if (after calculating) we see that dY (therefore dX) is negative?
Answer: this is impossible, the EXAMINER is responsible for NOT OCCURING that, you don´t need to waste time checking!!
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by diebeatsthegmat » Thu Oct 21, 2010 7:16 pm
goyalsau wrote:HI! Guys

[spoiler]OA is this question is D,
They are making equation from the statements as
x - 6000 = 4.5 ( y - 6000 ) and then using the x = 3y

Same with II statement.
I want to know , X and Y is mileage , How can we subtract miles driven from the mileage ..

WHAT IS THE LOGIC

I am totally confused Please Help....[/spoiler]
hey, whats the source?
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by goyalsau » Sat Oct 23, 2010 9:24 pm
diebeatsthegmat wrote: hey, whats the source?
Grockit.....free practice question.
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