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Re: Which of the following is NOT a factor of the product of the [#permalink]
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Firstly the product of first positive 50 multiples of 4=>
4*1*4*2*4*3*4*4*4*5.....4*50=> 4^50*50!
Secondly notice Option D is 47^2 and 47 is a prime number.
Number of 47's in 4^50*50!=> one
Hence 47^2 will never be its factor.

Hence D.
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Re: Which of the following is NOT a factor of the product of the [#permalink]
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Hi Bunuel
Can you please give your explanation for this question..All the 50 multiples of 4 would be even, then how come 17 is a factor of this product?
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Re: Which of the following is NOT a factor of the product of the [#permalink]
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Shiv2016 wrote:
Hi Bunuel
Can you please give your explanation for this question..All the 50 multiples of 4 would be even, then how come 17 is a factor of this product?


My solution would be the same as this one: https://gmatclub.com/forum/which-of-the ... l#p1257006
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Re: Which of the following is NOT a factor of the product of the [#permalink]
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Shiv2016 wrote:
Hi Bunuel
Can you please give your explanation for this question..All the 50 multiples of 4 would be even, then how come 17 is a factor of this product?


Also, are you saying that even number cannot have an odd factor? It's not true. For example, 4*17 = 68 is even and is a multiple of 17.
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Re: Which of the following is NOT a factor of the product of the [#permalink]
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gmatpapa wrote:
Which of the following is NOT a factor of the product of the first 50 positive multiples of 4 ?

A. \(17^2\)
B. \(11^4\)
C. \(7^6\)
D. \(47^{12}\)
E. \(2^{124}\)


Since the first positive multiple of 4 is 4 and the 50th is 200, we see that in the product of the numbers of:

4 x 8 x 12 x 16…..x 196 x 200, we won’t have 12 factors of 47, and thus, 47^12 is not a factor of the first 50 multiples of 4. (Note: 47 is prime, and in the product 4 x 8 x 12 x 16…..x 196 x 200, there is only one factor of 47, which is in 188.)

Answer: D
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Re: Which of the following is NOT a factor of the product of the [#permalink]
Hi,

Can some please explain how can the below quoted portion

Quote:
product of the first 50 positive multiples of 4 = 4*8*12*16*......200


Equal to

Quote:
4^50*(1*2*3......49*50) = 2^100(FACTORIAL 50)


Without skipping any simplification steps?

Thanks in advance!
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Re: Which of the following is NOT a factor of the product of the [#permalink]
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Rebaz wrote:
Hi,

Can some please explain how can the below quoted portion

Quote:
product of the first 50 positive multiples of 4 = 4*8*12*16*......200


Equal to

Quote:
4^50*(1*2*3......49*50) = 2^100(FACTORIAL 50)


Without skipping any simplification steps?

Thanks in advance!


hey there Rebaz

for Example Factorial 50! means 1*2*3*4*....50

since we need to find product of first 50 multiples of 4 so basically you multiply 4 by consecutive first 50 numbers (4*1, 4*2, 4*3, 4*4 ....* 4*50) which is the same as \(4^{50}*(1*2*3......49*50)\) or \(2^{100} *50!\)

:)

hi Bunuel, this question is tagged both as kaplan and OG, i wonder from which source is the question :grin:
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Re: Which of the following is NOT a factor of the product of the [#permalink]
dave13

Thank you for your clear explanation!
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Which of the following is NOT a factor of the product of the [#permalink]
4 x 8 x 12 x...........x200 = 4^50(50!), now looking on 50! i.e (1 x 2 x 4 x.....x 50) separately, which comprises of two 17s (17, 34 (17 x2), four 11s (11, 22, 33,44), eight 7s (7,14,21,28,35,42 and 49 (49 = 7 x7) and on a similar manner number of twos in 50! would be (25 (2s)+ 12 (4s)+ 6 (8s)+ 3 (16s)+ 1(32s) = 47 ) + 2s in in 4^50 (=2^100 = 100), therefore total of 147. But for 47 there is only one factor of 47 (<50) which is 47.

Any number beyond the accounted #s (on power) is not a factor. Be it either 17^3 or 11^5 or 7^9 or 2^148 or even 47^2. Hence D.
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Re: Which of the following is NOT a factor of the product of the [#permalink]
blueseas wrote:
gmatpapa wrote:
Which of the following is NOT a factor of the product of the first 50 positive multiples of 4 ?

A. \(17^2\)
B. \(11^4\)
C. \(7^6\)
D. \(47^{12}\)
E. \(2^{124}\)



product of the first 50 positive multiples of 4 = 4*8*12*16*......200 =4^50*(1*2*3......49*50) = 2^100(FACTORIAL 50)

lets check options:

A. \(17^2\) ==>we need two 17 ==>that can be found in FACTORIAL 50 (17,34)=>factor

B. \(11^4\) ==>we need four 11==> that can be found in FACTORIAL 50 (11,22,33,44)=>factor

C. \(7^6\) ==>we need six 7 ==>that can be found in FACTORIAL 50(7,14,21,28,35,42)=>factor

D. \(47^{12}\)==>not a factor since we 47 is a prime and is only 1 time present in factorial 50

E. \(2^{124}\)==>This can be found as we have 2 ^100 and in factorial 50 we have 25 even numbers=>factor

hence D


I thought it mentioned first 50 MULTIPLES of 4?not 50!?so its 4, 8, 12, ..., 200?
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Re: Which of the following is NOT a factor of the product of the [#permalink]
Can anyone help me in explaining why option E is correct ?
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Re: Which of the following is NOT a factor of the product of the [#permalink]
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GMATBUDDING wrote:
Which of the following is NOT a factor of the product of the first 50 positive multiples of 4 ?

A. \(17^2\)
B. \(11^4\)
C. \(7^6\)
D. \(47^{12}\)
E. \(2^{124}\)

Can anyone help me in explaining why option E is correct ?



The product of the first 50 positive multiples of 4 is \(4*8*12*...*200 = 4^{50}(1*2*3*...*50) = 2^{100}*50!\).

To find the power of 2 in the prime factorization of 50!, we use the formula: 50/2 + 50/4 + 50/8 + 50/16 + 50/32 = 25 + 12 + 6 + 3 + 1 = 47 (only the quotients of the divisions are considered, for example, 50/16 = 3). Thus, \(2^{100}*50!=2^{100}*2^{47}*something=2^{147}*something\), which is divisible by 2^124.

For theory check: Number Properties

For questions check the following topics from our Special Questions Directory:

12. Trailing Zeros
13. Power of a number in a factorial

For more check Ultimate GMAT Quantitative Megathread

Hope it helps.
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Re: Which of the following is NOT a factor of the product of the [#permalink]
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