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# If j is a multiple of 12, and k is a multiple of 21, then jk must be a

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Math Expert
Joined: 02 Sep 2009
Posts: 58445
If j is a multiple of 12, and k is a multiple of 21, then jk must be a  [#permalink]

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31 Oct 2018, 00:56
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Difficulty:

15% (low)

Question Stats:

82% (01:07) correct 18% (01:00) wrong based on 44 sessions

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If j is a multiple of 12, and k is a multiple of 21, then jk must be a multiple of which of the following?

A. 8
B. 15
C. 22
D. 28
E. 35

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VP
Joined: 31 Oct 2013
Posts: 1465
Concentration: Accounting, Finance
GPA: 3.68
WE: Analyst (Accounting)
Re: If j is a multiple of 12, and k is a multiple of 21, then jk must be a  [#permalink]

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31 Oct 2018, 01:13
Bunuel wrote:
If j is a multiple of 12, and k is a multiple of 21, then jk must be a multiple of which of the following?

A. 8
B. 15
C. 22
D. 28
E. 35

j = 12k

k = 21k

Lcm of 12 and 21 : 84 ...........the minimum value of jk

28 * 3 = 84.
Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 9706
Location: Pune, India
Re: If j is a multiple of 12, and k is a multiple of 21, then jk must be a  [#permalink]

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31 Oct 2018, 02:29
Bunuel wrote:
If j is a multiple of 12, and k is a multiple of 21, then jk must be a multiple of which of the following?

A. 8
B. 15
C. 22
D. 28
E. 35

j = 12a
k = 21b

$$jk = 12*21 * a * b = 2^2 * 3^2 * 7 * ab$$

The option which is a factor of 2^2 * 3^2 * 7 will be correct.
$$28 = 2^2 * 7$$

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Karishma
Veritas Prep GMAT Instructor

Re: If j is a multiple of 12, and k is a multiple of 21, then jk must be a   [#permalink] 31 Oct 2018, 02:29
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