From the stimulus, X must contain factors of 2 and 3, and Y 2 and 7.
Multiple of 105 must contain factors of 5, 3, and 7, and we already know that XY contains factors of 3 and 7.
So before we even read (1) and (2), we should already know to look for any sign of X or Y containing factor of 5.
1) Insufficient, because we're still missing factor of 5.
2) Sufficient, Y contains at least 2 factors of 5.
Answer is B.
Number Theory question
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euro
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To me, this appears to be a YES & NO question.... is XY a mutiple of 105?uwhusky wrote:From the stimulus, X must contain factors of 2 and 3, and Y 2 and 7.
Multiple of 105 must contain factors of 5, 3, and 7, and we already know that XY contains factors of 3 and 7.
So before we even read (1) and (2), we should already know to look for any sign of X or Y containing factor of 5.
1) Insufficient, because we're still missing factor of 5.
2) Sufficient, Y contains at least 2 factors of 5.
Answer is B.
So Statement (1) is also SUFFICIENT to answer the question (even though the answer may be a 'No')
IMO, answer should be (D) Each statement alone is sufficient.
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uwhusky
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With DS, you can't make assumptions such as what you're making with (1).
(1) says nothing of Y, and it is very possible that Y is indeed 25. So (1) is insufficient because XY could be multiple of 105 and it could be not.
It has to be always yes or always no in order to meet the DS requirement.
(1) says nothing of Y, and it is very possible that Y is indeed 25. So (1) is insufficient because XY could be multiple of 105 and it could be not.
It has to be always yes or always no in order to meet the DS requirement.
Yep.
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GMATGuruNY
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105 = 3*5*7gig92 wrote:If positive integer X is a multiple of 6 and positive integer Y is a mutiple of 14, is XY a mutiple of 105?
1) X is a mutiple of 9
2) Y is a multiple of 25
What do you think?
For xy to be a multiple of 105, it must be divisible by 3, 5 and 7.
x is a multiple of 6, so x is divisible by 2 and 3. Thus xy is divisible by 3.
y is a multiple of 14, so y is divisible by 2 and 7. Thus xy is divisible by 7.
What we don't know is whether xy is divisible by 5. The question becomes: Is x or y divisible by 5?
Statement 1:
No information about whether x or y is divisible by 5. Insufficient.
If x = 54 and y = 14, is x or y divisible by 5? No.
If x = 90 and y = 14, is x or y divisible by 5? Yes.
Statement 2:
If y is a multiple of 25, then y is divisible by 5.
Sufficient.
The correct answer is B.
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gig92
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GMATGuruNY wrote:105 = 3*5*7gig92 wrote:If positive integer X is a multiple of 6 and positive integer Y is a mutiple of 14, is XY a mutiple of 105?
1) X is a mutiple of 9
2) Y is a multiple of 25
What do you think?
For xy to be a multiple of 105, it must be divisible by 3, 5 and 7.
x is a multiple of 6, so x is divisible by 2 and 3. Thus xy is divisible by 3.
y is a multiple of 14, so y is divisible by 2 and 7. Thus xy is divisible by 7.
What we don't know is whether xy is divisible by 5. The question becomes: Is x or y divisible by 5?
Statement 1:
No information about whether x or y is divisible by 5. Insufficient.
If x = 54 and y = 14, is x or y divisible by 5? No.
If x = 90 and y = 14, is x or y divisible by 5? Yes.
Statement 2:
If y is a multiple of 25, then y is divisible by 5.
Sufficient.
The correct answer is B.
Yes, it's B
gig92
