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What is the hundredths digit in the decimal expression of

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What is the hundredths digit in the decimal expression of [#permalink] New post 15 Nov 2010, 15:38
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A
B
C
D
E

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Question Stats:

47% (01:54) correct 53% (01:08) wrong based on 126 sessions
What is the hundredths digit in the decimal expression of x/55

(1) x is the least common denominator of 1/7 and positive integer y
(2) x is prime.
[Reveal] Spoiler: OA

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Last edited by rxs0005 on 15 Nov 2010, 16:10, edited 1 time in total.
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Re: Arithmetic tough DS [#permalink] New post 15 Nov 2010, 16:02
Hey RXS:

Can you retype Statement 1? You're missing the number/variable before "and", so it's tough to make sense of statement 1.

2 alone is not sufficient, so we can at least get started with that!

Thanks!
Brian
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Re: Arithmetic tough DS [#permalink] New post 15 Nov 2010, 17:13
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Thank you!

Just one more clarification...I don't think you can have a "least common denominator" of a positive integer, so I'm going to treat this one as:

1) x is the least common denominator of 1/7 and 1/y (with y as a positive integer)

If that's the case, 1 isn't sufficient on its own, as x could be 7, 14, 21, etc. And if you look at what the decimals would be of x/55:

7/55 will be something really small (less than 1/7 and just over 1/8, so maybe around .13)

14/55 will just double that (so maybe around .27)

21/55 will triple the original (.3-something)

So we can tell that the hundredths digit will be different depending on which multiple of 7 x turns out to be.

Together, though, if x is a prime number that's the lowest common denominator of y and 7, then x must be 7 (anything else divisible by 7 is not prime). So x/55 = 7/55, and whatever that hundredths digit turns out to be, there will only be one. So the answer here would be C.
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Re: Arithmetic tough DS [#permalink] New post 16 Nov 2010, 09:21
Could this be a trick question?

While you can't really have a lowest common denominator for an integer y, but you can represent y as y/1 which would yield a lowest common denominator of 7.
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Re: Arithmetic tough DS [#permalink] New post 16 Nov 2010, 11:09
Guys the OA is A for this Bunuel can u help us on this , from what i gather u can have LCD of a fraction and an integer
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Re: Arithmetic tough DS [#permalink] New post 16 Nov 2010, 14:38
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rxs0005 wrote:
What is the hundredths digit in the decimal expression of x/55

(1) x is the least common denominator of 1/7 and positive integer y
(2) x is prime.


If statement (1) is as you wrote and OA is A then:

(1) x is the least common denominator of 1/7 and positive integer y --> if x is the least common denominator of 1/7 and y/1 (where y is a positive integer) then x must equal to 7 (7 is a least common multiple of 7 and 1), so we can find the hundredths digit of 7/55. Sufficient.
(2) x is prime. Clearly insufficient.

Answer: A.
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Re: Arithmetic tough DS [#permalink] New post 27 Apr 2011, 00:25
rxs0005 wrote:
What is the hundredths digit in the decimal expression of x/55

(1) x is the least common denominator of 1/7 and positive integer y
(2) x is prime.


Bit strange, y can be also written as 14/7, 28/14 or so,giving an integral value.
In that case LCD becomes 7 or more.
Considering this scenario, b definitely comes into picture.
OA becomes C then.
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Re: Arithmetic tough DS [#permalink] New post 27 Apr 2011, 00:43
amit2k9 wrote:
rxs0005 wrote:
What is the hundredths digit in the decimal expression of x/55

(1) x is the least common denominator of 1/7 and positive integer y
(2) x is prime.


Bit strange, y can be also written as 14/7, 28/14 or so,giving an integral value.
In that case LCD becomes 7 or more.
Considering this scenario, b definitely comes into picture.
OA becomes C then.


If it is written that "y" is +ve integer, it means that y is integer in its simplest form. What you have written is correct but is not in its simplest form.

BTW, I liked VeritasPrepBrian's tweak in the question. Made it more interesting.
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Re: Arithmetic tough DS [#permalink] New post 05 Sep 2011, 11:29
Quote:
What is the hundredths digit in the decimal expression of x/55

(1) x is the least common denominator of 1/7 and positive integer y
(2) x is prime.



From Statement 1
Least common denominator of 1/7 and positive integer Y/1 ---> 7
So, x=7
Sufficient

From Statement 2
possible values of x ---> all prime nos.
Insufficient

Answer: A
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Re: Arithmetic tough DS   [#permalink] 05 Sep 2011, 11:29
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