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Data sufficiency question query

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Data sufficiency question query

by moindanawala » Sun Sep 09, 2012 9:13 am
Hey Guys,

I have been practicing a couple of data sufficiency questions lately and came across a question which i found to have a solution other than the source provided, can you please help me by looking into this if possible, i have attached the question

If a, b, and c are positive, is ac>5?

(1)a+b=3

(2)4=c-b

Would look forward to hear from you on the solution and the answer when possible, thanks

Regards
Moi
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Source: — Data Sufficiency |
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by KapilKapoor » Sun Sep 09, 2012 9:29 am
St1: Not sufficient
St2: Not sufficient

Both

a+c=7
We know that Arithmetic mean >= Geometric mean
(a+c)/2 >= sqrt(ac)
3.5 >= sqrt (ac)

ac can be less than or more than 5. Not sufficient

Ans: E

Regards,
Kapil
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by Brent@GMATPrepNow » Sun Sep 09, 2012 9:47 am
moindanawala wrote:Hey Guys,

If a, b, and c are positive, is ac>5?
(1)a+b=3
(2)4=c-b
Target question: Is ac > 5?
Since each statement is missing either a or c, let's jump straight to . . .

Statements 1 & 2 combined
If a+b=3 and 4=c-b, then there are many possible case to consider. Here are two.
case a: a=1, b=2, c=6, in which case ac is greater than 5
case b: a=0.1, b=2.9, c=6.9, in which case ac is not greater than 5
Since we have two conflicting answers to the target question, the answer is E

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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