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For a,b,d are the positive integers, and d|a means that “a is divisibl

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For a,b,d are the positive integers, and d|a means that “a is divisibl  [#permalink]

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New post 11 Feb 2016, 23:02
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

76% (01:30) correct 24% (01:39) wrong based on 96 sessions

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For a,b,d are the positive integers, and d|a means that “a is divisible by d”, if d|ab, which of the following must be true?

A. d|a
B. d|b
C. d|2ab
D. d|(a+b)
E. d|(a-b)


* A solution will be posted in two days.

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Re: For a,b,d are the positive integers, and d|a means that “a is divisibl  [#permalink]

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New post 12 Feb 2016, 00:56
d/a means a is divisible by d

d/ab means ab divisible by d.

all are integers so ,

if ab is divisible by d,

1 a can be divisible by d
or
2 b can be divisble by d.

so the question stem asks must true.

so option a and b are could but not must.

option c is 2ab divisible by d. if ab is divisible by d then 2ab is divisible by d.
option d and e we can't predict.


so option C is correct.
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Re: For a,b,d are the positive integers, and d|a means that “a is divisibl  [#permalink]

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New post 13 Feb 2016, 22:38
For a,b,d are the positive integers, and d|a means that “a is divisible by d”, if d|ab, which of the following must be true?

A. d|a
B. d|b
C. d|2ab
D. d|(a+b)
E. d|(a-b)


--> d|ab is ab=dk(k=integer) and also 2ab=2dk can be divided by d.
Therefore, the answer is C.
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Re: For a,b,d are the positive integers, and d|a means that “a is divisibl  [#permalink]

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New post 04 Mar 2016, 17:26
HI MathRevolution,

MathRevolution wrote:
For a,b,d are the positive integers, and d|a means that “a is divisible by d”, if d|ab, which of the following must be true?

A. d|a
B. d|b
C. d|2ab
D. d|(a+b)
E. d|(a-b)


--> d|ab is ab=dk(k=integer) and also 2ab=2dk can be divided by d.
Therefore, the answer is C.


d/ab = k => dk = ab. I dont know how could you give conclusion that ab= dk?
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Re: For a,b,d are the positive integers, and d|a means that “a is divisibl  [#permalink]

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New post 07 Mar 2016, 16:34
oanhnguyen1116 wrote:
HI MathRevolution,

MathRevolution wrote:
For a,b,d are the positive integers, and d|a means that “a is divisible by d”, if d|ab, which of the following must be true?

A. d|a
B. d|b
C. d|2ab
D. d|(a+b)
E. d|(a-b)


--> d|ab is ab=dk(k=integer) and also 2ab=2dk can be divided by d.
Therefore, the answer is C.


d/ab = k => dk = ab. I dont know how could you give conclusion that ab= dk?



-> Because ab is divisible by d.
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Re: For a,b,d are the positive integers, and d|a means that “a is divisibl  [#permalink]

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New post 08 Mar 2016, 00:26
Thank you MathRevolution :)
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Re: For a,b,d are the positive integers, and d|a means that “a is divisibl  [#permalink]

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New post 14 Mar 2016, 05:55
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Re: For a,b,d are the positive integers, and d|a means that “a is divisibl  [#permalink]

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Re: For a,b,d are the positive integers, and d|a means that “a is divisibl   [#permalink] 26 Dec 2018, 11:17
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