MST 1 Quantitative Analysis Section 2 Question 7

[okoronkwoac]

After taking MST1, I decided to go through the solution and I disagree with the solution for Q7 Section2. See an adaptation of the question and solution given below.

(X+8)(X-8) = 0
(Y+8)(Y-8)=0

We are required to compare (X+8) and (Y+8)

The solution given was concluded by saying that (X+8) = 16 or 0
and (Y+8) = -16 or 0, and thus option D was chosen as the answer.

That's exactly what I disagree with. Because Y = 8 or -8, Y+8 is also equal to 16 or 0.

Please take a look at this solution again.

[tommywallach]

Hey Okoronk,

I'm afraid you're thinking about it wrong. It might pay to go through the basic rules of QC again, because this represents a misunderstanding of what you're being asked.

X = 8 or -8
Y = 8 or -8

Column A: (X + 8) = 0 or 16

Column B: (Y + 8) = 0 or 16

Now, recognize what the answer choices in QC stand for:

(A) Column A is always bigger than the quantity in Column B
(B) Column B is always bigger than the quantity in Column A
(C) The two quantities are always equal

In this case, the two columns could both be 0 or both be 16, in which case the columns would be equal. However, Column A could be 16 and Column B could be 0, in which case Column A is bigger. By the same token, Column A could be zero and Column B could be 16, in which case Column B is bigger. So the answer is (D).

Seen more simply:

A: 0 B: 0 ---> A = B
A: 16 B: 16 ---> A = B
A: 16 B: 0 ---> A > B
A: 0 B: 16 --> A < B

The answer is (D) because all of these are viable.

Hope that helps!

-t

[pavya.c]

Hi,

The solution for the problem explained here is right and ans choice is d, but the solution which is given to us as y=-16,0 should be given as y=16,0 so when x= 16,0 and y=16,0 the above explanation will be right and will yield ans as d. I think the confusion is with the -ve sign in y. Is my understanding right?

Thanks

[tommywallach]

Hey Pavya,

Indeed, the explanation does seem to say that incorrectly (I've corrected it in our CATs now). However, that would not change the answer to the question.

Column A: 0 or 16
Column B: -16 or 0

In this case, the two columns could be equal (both zero) or not equal (one is 16, the other is -16, as one example), so the answer would still be (D).

However, you're totally right that it's confusing. : )

-t

[okoronkwoac]

Hey Okoronk,

I'm afraid you're thinking about it wrong. It might pay to go through the basic rules of QC again, because this represents a misunderstanding of what you're being asked.

X = 8 or -8
Y = 8 or -8

Column A: (X + 8) = 0 or 16

Column B: (Y + 8) = 0 or 16

Now, recognize what the answer choices in QC stand for:

(A) Column A is always bigger than the quantity in Column B
(B) Column B is always bigger than the quantity in Column A
(C) The two quantities are always equal

In this case, the two columns could both be 0 or both be 16, in which case the columns would be equal. However, Column A could be 16 and Column B could be 0, in which case Column A is bigger. By the same token, Column A could be zero and Column B could be 16, in which case Column B is bigger. So the answer is (D).

Seen more simply:

A: 0 B: 0 ---> A = B
A: 16 B: 16 ---> A = B
A: 16 B: 0 ---> A > B
A: 0 B: 16 --> A < B

The answer is (D) because all of these are viable.

Hope that helps!

-t

I definitely agree that the answer is D. Just that as in the solution given, Y will never be -16. This is the part I disagree with.

[okoronkwoac]

Hi,

The solution for the problem explained here is right and ans choice is d, but the solution which is given to us as y=-16,0 should be given as y=16,0 so when x= 16,0 and y=16,0 the above explanation will be right and will yield ans as d. I think the confusion is with the -ve sign in y. Is my understanding right?

Thanks

That's exactly my point.

[tommywallach]

Hey Okoronk,

Sorry if I misunderstood you. I thought it would be fairly clear that this was just a typo. So if you spot a typo, just write up on the forums: "Hey guys! You have a typo in your book!" The way you talked about it, it seemed like you were taking issue with the answer, which remains (D) either way.

-t