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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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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.

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.

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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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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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: What is the hundredths digit in the decimal expression of [#permalink]

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24 Aug 2015, 12:24

Bunuel 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.

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.

You assumed Y is an integer, so what we should do on actual GMAT ? assume uknowns like y are integers? always?

Re: What is the hundredths digit in the decimal expression of [#permalink]

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22 Oct 2017, 06:05

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