GCD and LCM

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g.shankaran: Master | Next Rank: 500 Posts; Posts: 101; Joined: Tue Oct 27, 2009 8:19 am; Thanked: 4 times; Followed by:2 members

GCD and LCM

by g.shankaran » Sun Jun 05, 2011 1:48 am

x and y are positive integers.what is the value of xy?

1. Greatest common factor of x and y is 10
2. Least common multiply of x and y is 180

C.

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Source: Beat The GMAT — Data Sufficiency | Sun Jun 05, 2011 1:48 am

g.shankaran: Master | Next Rank: 500 Posts; Posts: 101; Joined: Tue Oct 27, 2009 8:19 am; Thanked: 4 times; Followed by:2 members

by g.shankaran » Sun Jun 05, 2011 1:51 am

Please correct me if my understanding/calculation is wrong

1. GCD 10 - Insufficient
2. lcm 180 - insufficient.

1 & 2 - GCD is 10 - so both x and y has 10 in common

lcm 180 - 3 x 3 x 2 x 2 x 5

so the xy = 3 x 3 x 2 x 2 x 5 x 2 x 5 = 1800

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Frankenstein: Legendary Member; Posts: 1448; Joined: Tue May 17, 2011 9:55 am; Location: India; Thanked: 375 times; Followed by:53 members

by Frankenstein » Sun Jun 05, 2011 1:56 am

g.shankaran wrote:Please correct me if my understanding/calculation is wrong

1. GCD 10 - Insufficient
2. lcm 180 - insufficient.

1 & 2 - GCD is 10 - so both x and y has 10 in common

lcm 180 - 3 x 3 x 2 x 2 x 5

so the xy = 3 x 3 x 2 x 2 x 5 x 2 x 5 = 1800

Hi,
Correct.
The product of any two numbers X and Y is always equal to the product of their LCM and GCD.

Cheers!

Things are not what they appear to be... nor are they otherwise

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cans: Legendary Member; Posts: 1309; Joined: Mon Apr 04, 2011 5:34 am; Location: India; Thanked: 310 times; Followed by:123 members; GMAT Score:750