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ds doubt

by rakesheval » Tue Jun 24, 2008 12:03 pm

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Q. The operation* represents either addition, subtraction, or multiplication of integers,
what is the value of 1*0?
(1) 0*2=2
(2) 2*0=2

a. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient
b. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient
c. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE
is sufficient.
d. EACH statement ALONE is sufficient
e. Statements (1) and (2) TOGETHER are NOT sufficient

OA is A.
But my answer is D. My reasoning - From the second statement it is evident that either its a subtraction or an addition. In both the cases, 1*0 will be 1 only. Anyone with me?
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by egybs » Tue Jun 24, 2008 2:10 pm

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agreed...

where is this question from?
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by wawatan » Tue Jun 24, 2008 3:02 pm

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i agree with D. what the hell is wrong with statement B???? where did u get this question from?
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by rakesheval » Tue Jun 24, 2008 11:55 pm

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thanks for your answers.. this question is from one of the paper-based GMAT (atleast that's what the document claims :roll: )..
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by AleksandrM » Wed Jun 25, 2008 9:29 am

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Statement 1 alone is sufficient.

If 0*2 = 2 then it is definitely an addition. Otherwise the answer would be 0 or -2 [don't forget that 0 - 2 = -2].

For the second statement you arenot sure what the operation is:

2 - 0 = 2

2 + 0 = 2

Choose A.
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by egybs » Wed Jun 25, 2008 10:27 am

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Reread the question.. it isn't asking you what the operation is... it's asking you for the answer.


With statement 2, we know that it is either addition or subtraction...

Either way, 1+0 or 1-0 = 1... So both are sufficient to answer the question!


AleksandrM wrote:Statement 1 alone is sufficient.

If 0*2 = 2 then it is definitely an addition. Otherwise the answer would be 0 or -2 [don't forget that 0 - 2 = -2].

For the second statement you arenot sure what the operation is:

2 - 0 = 2

2 + 0 = 2

Choose A.
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by AleksandrM » Wed Jun 25, 2008 2:03 pm

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egybs,

I see what you are saying, and I am aware of the fact that we are being asked for the value of 1*0. However, in DS, of both statements are sufficient, then they should both yield the same answer. In the first case, we know that it is definitely addition. In the second case it could be either addition or subtraction. Yes, this is enough to answer the question as it is stated. However, I highly doubt that on the real test you will see a question that will allow for * to have two meanings and still answer the question.

I stick to my A.
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by egybs » Wed Jun 25, 2008 2:22 pm

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Aleks -

I think we can both agree that this is a bad question....

HOWEVER, the question asks us for the value of 1*0. Which we can determine with statement 2. We know, with 100% certainty, that the answer will be 1.

Furthermore, the two statements don't contradict each other... Statement 1 tells us that the * is addition, while statement 2 tells us that * is either addition or subtraction. It turns out we don't need to know which of the two it is. They both give the same answer. So it's sufficient.

Think of another type of question where this kind of logic exists:

What is X^2?

1) X = -2
2) X^4 = 16

Statement 1 definitively tells us that x^2 will be 4... and we know that x is -2.
Statement 2 doesn't tell us whether x is negative or positive... but it doesn't matter, because either way, x^2 will be equal to 4.

So both would be sufficient.

My guess is that there was a typo with the question... they probably typed 1*0 instead of 0*1. If the question had asked for the value of 0*1, then indeed statement 2 would be insufficient.
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by AleksandrM » Wed Jun 25, 2008 5:01 pm

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egybs, I agree with every word you said. I hope we can agree that this is a tie. :)
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Re: ds doubt

by Brent@GMATPrepNow » Fri Oct 29, 2021 10:07 am

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rakesheval wrote: ↑
Tue Jun 24, 2008 12:03 pm
 Q. The operation* represents either addition, subtraction, or multiplication of integers,
what is the value of 1*0?
(1) 0*2=2
(2) 2*0=2

a. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient
b. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient
c. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE
is sufficient.
d. EACH statement ALONE is sufficient
e. Statements (1) and (2) TOGETHER are NOT sufficient
This is an official GMAT question, and the correct answer is D.

Given: The operation * represents either addition, subtraction, or multiplication

Target question: What is the value of 1*0?

Statement 1: 0*2 = 2
Let's test all 3 possible operations:
0 + 2 = 2
0 - 2 = -2
0 x 2 = 0
We can see that * represents addition, which means the answer to the target question is 1*0 = 1+0 = 0
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: 2*0 = 2
Let's test all 3 possible operations:
2 + 0 = 2
2 - 0 = 2
2 x 0 = 0
We can see that * represents EITHER addition OR substitution.
Does this mean statement 2 is insufficient?
We don't know yet, since we haven't tried answering the target question yet.

Let's consider both possible cases:
Case a: * represents addition. In this case, the answer to the target question is 1*0 = 1+0 = 0
Case b: * represents subtraction. In this case, the answer to the target question is 1*0 = 1-0 = 0
So, even though we don't know which operation * represents, we can still answer the target question with certainty (1*0 definitely equals 0)
So, statement 2 is SUFFICIENT

Answer: D
Brent Hanneson - Creator of GMATPrepNow.com
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