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If x and y are integers x = (2)(3)(4)(5)(7)(11)(13)/(39y) and which

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Joined: 02 Sep 2009
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If x and y are integers x = (2)(3)(4)(5)(7)(11)(13)/(39y) and which  [#permalink]

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New post 13 Jul 2018, 00:49
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  15% (low)

Question Stats:

80% (01:35) correct 20% (01:41) wrong based on 50 sessions

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Re: If x and y are integers x = (2)(3)(4)(5)(7)(11)(13)/(39y) and which  [#permalink]

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New post 13 Jul 2018, 01:39
1
2
Bunuel wrote:
If x and y are integers \(x = \frac{(2)(3)(4)(5)(7)(11)(13)}{39y}\) and which of the following could be the value of y ?

A) 15
B) 28
C) 38
D) 64
E) 143


The first step is to prime factorize 39, which is 3*13. Now, the
remaining integers contained in y can only be a multiple of 2,4,5,7, or 11.

Evaluating answer options to check which is a possible value of y

A) 15 = 3*5 (Not possible)
B) 28 = 4*7 (Possible)
C) 38 = 2*19 (Not possible)
D) 64 = 4^2 (Not possible)
E) 143 = 13*11 (Not possible)
(Option B)
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Re: If x and y are integers x = (2)(3)(4)(5)(7)(11)(13)/(39y) and which  [#permalink]

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New post 13 Jul 2018, 03:37
1
Bunuel wrote:
If x and y are integers \(x = \frac{(2)(3)(4)(5)(7)(11)(13)}{39y}\) and which of the following could be the value of y ?

A) 15
B) 28
C) 38
D) 64
E) 143



Given

\(\frac{2*3*4*5*7*114*13}{39y}\)

= \(\frac{2*3*4*5*7*11*13}{3*13 *y}\)

= \(\frac{2*4*5*7*11}{y}\)

Thus y = 28. (28 = 4*7)

The best answer is B.
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Re: If x and y are integers x = (2)(3)(4)(5)(7)(11)(13)/(39y) and which  [#permalink]

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New post 25 Jul 2018, 10:17
1
pushpitkc wrote:
Bunuel wrote:
If x and y are integers \(x = \frac{(2)(3)(4)(5)(7)(11)(13)}{39y}\) and which of the following could be the value of y ?

A) 15
B) 28
C) 38
D) 64
E) 143


The first step is to prime factorize 39, which is 3*13. Now, the
remaining integers contained in y can only be a multiple of 2,4,5,7, or 11.

Evaluating answer options to check which is a possible value of y

A) 15 = 3*5 (Not possible)
B) 28 = 4*7 (Possible)
C) 38 = 2*19 (Not possible)
D) 64 = 4^2 (Not possible)
E) 143 = 13*11 (Not possible)
(Option B)



pushpitkc hello there world traveler :)

39 has 3 and 13 as prime numbers

in numerator we have (2)(3)(4)(5)(7)(11)(13)

i thought we need such number that would fill in missing prime numbers i mean 39 has 3 and 13 and correct answer choice 28 contains 4 and 7 ...BUT how about 5, and 11 shouldnt they be part of denominator ?? :? so that after division we have integer ? can you explain please :-)
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Joined: 26 Feb 2016
Posts: 3187
Location: India
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If x and y are integers x = (2)(3)(4)(5)(7)(11)(13)/(39y) and which  [#permalink]

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New post 25 Jul 2018, 21:30
1
dave13 wrote:
pushpitkc wrote:
Bunuel wrote:
If x and y are integers \(x = \frac{(2)(3)(4)(5)(7)(11)(13)}{39y}\) and which of the following could be the value of y ?

A) 15
B) 28
C) 38
D) 64
E) 143


The first step is to prime factorize 39, which is 3*13. Now, the
remaining integers contained in y can only be a multiple of 2,4,5,7, or 11.

Evaluating answer options to check which is a possible value of y

A) 15 = 3*5 (Not possible)
B) 28 = 4*7 (Possible)
C) 38 = 2*19 (Not possible)
D) 64 = 4^2 (Not possible)
E) 143 = 13*11 (Not possible)
(Option B)



pushpitkc hello there world traveler :)

39 has 3 and 13 as prime numbers

in numerator we have (2)(3)(4)(5)(7)(11)(13)

i thought we need such number that would fill in missing prime numbers i mean 39 has 3 and 13 and correct answer choice 28 contains 4 and 7 ...BUT how about 5, and 11 shouldnt they be part of denominator ?? :? so that after division we have integer ? can you explain please :-)


Hey dave13

I'm no world traveler - I was hoping you would be gracious enough
to sponsor my trip around the world :)

Now coming back to the problem.

The simple reason the numbers 5 and 11 are not contained in the
numerator is the reason we can't have 5 and 11 in the denominator.
The problem statement gives us that both x and y must be integers.
Therefore, if y = 5 or y = 11 the number x will become a non-integer

Let me explain by a small example:
Let the numerator be 546(which is prime-factorized as 2*3*7*13)
If we have 5 or 11 in the denominator, this will make the value of
the fraction a non-integer.

Hope this clears your confusion!
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If x and y are integers x = (2)(3)(4)(5)(7)(11)(13)/(39y) and which &nbs [#permalink] 25 Jul 2018, 21:30
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