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If a, b, and c are integers, what is the value of a?

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viveksharma247
 Post subject: If a, b, and c are integers, what is the value of a?
 Post Posted: Sun Sep 06, 2009 10:58 am 
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Students


Posts: 5
Seeking for some help to solve this GMAT prep DS problem:

If a, b, and c are integers, what is the value of a?

(i) (a-7)(b-7)(c-7) = 0
(ii) bc = 18

The answer as per GMAT prep is C.
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Kweku.Amoako
 Post subject: Re: If a, b, and c are integers, what is the value of a?
 Post Posted: Sun Sep 06, 2009 11:47 am 
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Posts: 47
1) if (a-7)(b-7)(c-7) = 0 and a,b,c are all integers then either (a-7) = 0 in which case a= 7 or (b-7)= 0 in which case b = 7 or (c-7) = 0 in which case c = 7. Not sufficient

2) ab = 7 says nothing about A so Insufficient

3) If a,b or c must be 7 and we know bc = 18(which is not multile of 7) then we know neither b nor c is equal 7 so a must be 7. Sufficient
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viveksharma247
 Post subject: Re: If a, b, and c are integers, what is the value of a?
 Post Posted: Sun Sep 06, 2009 12:19 pm 
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Students


Posts: 5
Thanks! I assumed that a=7 from (i). Thus, (ii) wasn't making any sense to me! Thanks for the great explanation.
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RonPurewal
 Post subject: Re: If a, b, and c are integers, what is the value of a?
 Post Posted: Fri Sep 25, 2009 11:44 pm 
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ManhattanGMAT Staff


Posts: 7146
Kweku.Amoako wrote:
1) if (a-7)(b-7)(c-7) = 0 and a,b,c are all integers then either (a-7) = 0 in which case a= 7 or (b-7)= 0 in which case b = 7 or (c-7) = 0 in which case c = 7. Not sufficient

2) ab = 7 says nothing about A so Insufficient

3) If a,b or c must be 7 and we know bc = 18(which is not multile of 7) then we know neither b nor c is equal 7 so a must be 7. Sufficient


excellent.
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