Source: Princeton Review
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
The OA is D
If j is a multiple of 12, and k is a multiple of 21, then jk must be a multiple...
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j is a multiple of 12BTGmoderatorLU wrote: ↑Wed Jul 01, 2020 5:55 amSource: Princeton Review
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
The OA is D
This means we can write j = 12n (for some integer n)
k is a multiple of 21
This means we can write k = 21m (for some integer m)
jk must be a multiple of which of the following?
jk = (12n)(21m)
= (4)(3)(n)(7)(3)(m)
= (28)(3)(n)(3)(m)
Clearly, jk is a multiple of 28
Answer: D
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Solution:BTGmoderatorLU wrote: ↑Wed Jul 01, 2020 5:55 amSource: Princeton Review
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
The OA is D
Since j is a multiple of 12 and k is a multiple of 21, jk must be a multiple of the LCM of 12 and 21 and all its factors. Since the LCM of 12 and 21 is 3 x 4 x 7 = 84 and one of its factors is 28, jk is a multiple of 28.
Answer: D
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