Least common multiple of x and 12

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bigguy_aug: Junior | Next Rank: 30 Posts; Posts: 11; Joined: Fri Mar 26, 2010 5:21 pm; Thanked: 1 times

by bigguy_aug » Sun Oct 24, 2010 10:52 am

What is the least common multiple of x and 12?

1. The least common multiple of x and 9 is 45
2. The least common multiple of x and 4 is 20

Please explain your answer.

Thanks

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Source: Beat The GMAT — Data Sufficiency | Sun Oct 24, 2010 10:52 am

shovan85: Community Manager; Posts: 991; Joined: Thu Sep 23, 2010 6:19 amFollowed by: 24 members; Location: Bangalore, India; Thanked: 146 times

by shovan85 » Sun Oct 24, 2010 11:00 am

bigguy_aug wrote:What is the least common multiple of x and 12?

1. The least common multiple of x and 9 is 45
2. The least common multiple of x and 4 is 20

Please explain your answer.

Thanks

from 1: LCM[x,9] = 45

x can be either 5 or 15 or 45

LCM [12,15] = 60
LCM [12,45] = 180

So not sufficient.

from 2: LCM[x,4] = 20

x can be 5 or 10

LCM [12,5] = 60
LCM [12,10] = 60

Thus sufficient.

IMO B

See although we get the differing value of x we get a concrete vale of the LCM with 12.

If the problem is Easy Respect it, if the problem is tough Attack it

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