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If positive integer n is divisible by both 4 and 21, then n must be di

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Bunuel
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If positive integer n is divisible by both 4 and 21, then n must be di [#permalink] New post   24 Mar 2016, 02:56
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If positive integer n is divisible by both 4 and 21, then n must be divisible by which of the following?

A. 8
B. 12
C. 18
D. 24
E. 48
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B
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ramyapilai
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Re: If positive integer n is divisible by both 4 and 21, then n must be di [#permalink] New post   24 Mar 2016, 05:23
A number divisible by both 4 & 21 is 84 which s divisible by 12.
IMO : Answer B 12


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RDhin
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Re: If positive integer n is divisible by both 4 and 21, then n must be di [#permalink] New post   31 Mar 2016, 03:00
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If positive integer n is divisible by both 4 and 21, then n must be divisible by which of the following?

Let me take somewhat basic approach

X is divisible by 4
X = 4x = factors {2,2}

X is divisible by 21
X= 7x = factors {3,7}

As all factors in this case are exclusive and nothing in common between
So minimum set of factors is { 2,2,3,7 }

This number thus must be divisible by 4 (given), 21 (given), {2,3} = 6 , {2,7}= 14 , {3,7} = 21 , {2,2,3} = 12 , {2,2,7} = 28 , {2,3,7} = 42 , {2,2,3,7}= 8

As per given options 12 seems right :)
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Re: If positive integer n is divisible by both 4 and 21, then n must be di [#permalink] New post   31 Mar 2016, 05:10
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Bunuel wrote:
If positive integer n is divisible by both 4 and 21, then n must be divisible by which of the following?

A. 8
B. 12
C. 18
D. 24
E. 48


N is divisible by 4 and 21 both.
This means N is divisible by the LCM (4,21) = 84

84 is divisible by 12.
Option B
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Re: If positive integer n is divisible by both 4 and 21, then n must be di [#permalink] New post   27 Jun 2017, 15:15
Bunuel wrote:
If positive integer n is divisible by both 4 and 21, then n must be divisible by which of the following?

A. 8
B. 12
C. 18
D. 24
E. 48


We can just shortcut this problem by multiplying 4 and 21- which equals 84. The question says must be divisible by 4 so if 84 is not divisible by an answer choice then we can cross off that answer choice. Applying this method, only 12 is left.

Thus
"B"
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Re: If positive integer n is divisible by both 4 and 21, then n must be di [#permalink]
27 Jun 2017, 15:15
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