What is the tenths digit in the decimal representation of a

SOLUTION

What is the tenths digit in the decimal representation of a certain number?

(1) The number is less than 1/3.

(2) The number is greater than 1/4.

Each statement alone is clearly insufficient. When taken together we have \(0.25<x<0.333...\). Hence the tenths digit can be 2 (for example if x= 0.251) or 3 (for example if x=0.3). Not sufficient.

Answer: E.
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lets assume N = 0.xyz...

(1)
N < 1/3
N < 0.333333

Now, N can be 0.234 or 0.3111 or 0.121212
Basically, tenths digit can be 0 or 1 or 2 or 3
So, we cant say what would be the tenths digit
hence not sufficient.

(2)
N > 1/4
N > 0.25
Now, here digit can be 2,3,4,5,6,7,8,9
Hence this is also not sufficient

combining (1) and (2), the tenths digit can be either 2 or 3.
So, we can't answer the exact digit.

Hence E

As I am going through the OG12 and other sources, I notice the use of when to consider a negitive (or similar) inconsistent during answer explainations from the question makers.

For example, today I came across this DS question:

OG12 question 43 page 276
What is the tenths digit in the decimal representation of a certain number?

1) the number is less than 1/3
2) the number is greater than 1/4

The OA states:

1) Since the number is less than 1/3, the tenths digit can be 0,1,2, or 3; NOT sufficient
2) Since the numebr is greater than 1/4, the tenths digit can be 2,3,4, ..., 9; NOT sufficient


My contention is that the OA doesn't take into consideration negitive numbers for S1, nor numbers greater than 1 for S2. Because of this, the tens digit could be any number 0-9 for either S1 or S2. Of course, in this question it doesn't affect the outcome of the correct answer being E; but I have seen questions inconsistently consider negitives or not

Any insight as to when to ignore negitives (or other bounds like non-integer/fractions) despite the question not stating it in any manner?

Thanks

Hey chetan2u i have a question regarding this official question.
The answer is clearly E but here is my doubt=>
the official guide says that that for statement 1 the unit digits can be 0 or 1 or 2 or 3
now what if the number is -2.55 or -198.67 My point being the negative numbers are possible too but why is not GMAT offical testmakers considering them ..
Similarly for statement two the tens digits can be 8 or 1 or 3 or anything as per me.

Just lemme know if i am missing something here ?


Regards
StoneCold
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hi,

I would say that we consider the negative too..
the Q nowhere mentions that the number is positive..
the GMAT nowhere says a decimal cannot be negative..
so may be the explanation has missed out on these numbers as the answer does not get affected..
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We need to determine the value of the tenths place of a particular number.

Statement One Alone:

The number is less than 1/3.

Since the number is less than 1/3, it is less than 0.333…. Thus, we could have values such as 0.3 (with a tenths place of 3) or 0.2 (with a tenths place of 2). Statement one is not sufficient to answer the question. We can eliminate answer choices A and D.

Statement Two Alone:

The number is greater than 1/4.

Since the number is greater than 1/4, it is greater than 0.25. Thus, we could have values such as 0.3 (with a tenths place of 3) or 0.4 (with a tenths place of 4). Statement two does not provide enough information to answer the question. We can eliminate answer choice B.

Statements One and Two Together:

From statements one and two we know that the decimal value is between 0.25 and 0.333…. We could still have decimals values with different tenths places, such as 0.28 or 0.3.

The answer is E.
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Target question: What is the tenths digit in the decimal representation of a certain number?

Statement 1: The number is less than 1/3
There are several values that satisfy statement 1. Here are two:
Case a: the number = 0.31, in which case the value of the tenths digit is 3.
Case b: the number = 0.298, in which case the value of the tenths digit is 2
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 1: The number is greater than 1/4
There are several values that satisfy statement 2. Here are two:
Case a: the number = 0.31, in which case the value of the tenths digit is 3.
Case b: the number = 0.298, in which case the value of the tenths digit is 2
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
IMPORTANT: Notice that I was able to use the same counter-examples to show that each statement ALONE is not sufficient. So, the same counter-examples will satisfy the two statements COMBINED.
In other words,
Case a: the number = 0.31, in which case the value of the tenths digit is 3.
Case b: the number = 0.298, in which case the value of the tenths digit is 2
Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT

Answer: E

Cheers,
Brent

Hello
Bunuel IanStewart
Can we consider 'negative' (e.g., -0.332) number when we explain statement 1?
Thanks__
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Technically, I suppose so, but I've never seen (and would bet I will never see) an official question about digits in which you'd ever need to think about negative numbers to get the right answer.
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Thank you so much for your response. May I have your reasoning on this ground, please? In short, why do you think so?
I appreciate your help sir!
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