Difficult DS

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m7373: Newbie | Next Rank: 10 Posts; Posts: 6; Joined: Tue Feb 05, 2008 2:46 pm

by m7373 » Sun Feb 24, 2008 3:00 pm

Please help with this DS question

Is a-3b an even number?

1) b=3a+3
2) b-a is an odd number

I would appreciate a detailed explanation.

thanks

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Source: Beat The GMAT — Data Sufficiency | Sun Feb 24, 2008 3:00 pm

its_me07: Senior | Next Rank: 100 Posts; Posts: 83; Joined: Mon Oct 22, 2007 4:44 am; Thanked: 1 times

by its_me07 » Mon Feb 25, 2008 3:25 am

OA is D

St 1 SUFF.
Plug in numbers in both the equations e.g take a=1 so b=6 now a - 3b becomes -17 () any number u plug in will give u an odd number so a-3b is not an even number

ST 2 SUFF

b-a=4-1=3
1-3(4)=-11

or -1-4=-5
-1 - 3(-4)=11

hence bith are SUFF.

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