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GMAT Powerprep -Number properties question

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by ssy » Sun Oct 28, 2007 4:41 am
If x and y are positive integers, is xy a multiple of 8?

1) Greatest common denominator of x and y is 10

2) Lowest common multiple of x and y is 100.

C, both statements together are sufficient

I cannot for the life of me figure out the implications of statement 2 :(
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Source: — Data Sufficiency |

by jangojess » Sun Oct 28, 2007 5:17 am
stmt 1 - i think it shld be Greatest Common Dvisior (GCD) which means the HCF (Highest Common Factor) of x and y is 10...insuff

stmt 2 - LCM is 100......insuff

Both - HCF is 10 and LCM is 100...Now the prod of 2 numbers = HCF * LCM = 1000, which is a multiple of 8.....Suff and so ans is C

This link will give u more insight on LCM and HCF

https://www.cimt.plymouth.ac.uk/projects ... k8_2i4.htm
Trying hard!!!
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by ssy » Mon Oct 29, 2007 5:26 am
As usual, thanks Jango Jess!

Just out of curiousity..what are two numbers which have an LCM of 100...?
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by naren_nayak » Thu Nov 01, 2007 8:48 am
4 & 25 have an LCM of 100.
And so do 20 & 50.
The former is divisible by 8, the latter is not.
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