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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: 50585
If j is a multiple of 12, and k is a multiple of 21, then jk must be a  [#permalink]

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30 Oct 2018, 23:56
1
00:00

Difficulty:

25% (medium)

Question Stats:

88% (00:46) correct 12% (01:31) wrong based on 25 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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Director
Joined: 31 Oct 2013
Posts: 777
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, 00:13
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: 8531
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, 01:29
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
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Re: If j is a multiple of 12, and k is a multiple of 21, then jk must be a &nbs [#permalink] 31 Oct 2018, 01:29
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