I find a very confusing question in Manhattan's algebra strategy book pg 115. Please Correct me if Im wrong.
if a=3bc, what is the value of c?
(1) a=10-b
(2) 3a = 4b
Manhattan answer: [spoiler]B: statement 2 itself is sufficient because : 3a=4b => a/b=4/3 => c= 1/3 x a/b = 1/3 * 4/3
[/spoiler]
However I think B is wrong, Because statement 2 leads to 2 results: a/b=4/3 OR b=a=0
in case a=b=0 => c can be any number => correct answer must be C: both statement together are sufficient but neither statement alone is sufficient.
A flaw in Manhattan GMAT question?
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Hi truck,
You are absolutely correct. For the answer to be B, an additional piece of information would need to be included, namely that none of the variables could equal 0. So there's either a typo in the question or the author made a mistake (and didn't account for the possibility of 0). Since GMAC goes through a rather rigorous testing process, the questions that you'll see on your Official GMAT won't have these sorts of errors in them.
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You are absolutely correct. For the answer to be B, an additional piece of information would need to be included, namely that none of the variables could equal 0. So there's either a typo in the question or the author made a mistake (and didn't account for the possibility of 0). Since GMAC goes through a rather rigorous testing process, the questions that you'll see on your Official GMAT won't have these sorts of errors in them.
GMAT assassins aren't born, they're made,
Rich
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A perfect example of why "what about 0?" is an important thought in DS.
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Thank you so much, your response makes me feel much more confident now.
Cheers!
Cheers!
[email protected] wrote:Hi truck,
You are absolutely correct. For the answer to be B, an additional piece of information would need to be included, namely that none of the variables could equal 0. So there's either a typo in the question or the author made a mistake (and didn't account for the possibility of 0). Since GMAC goes through a rather rigorous testing process, the questions that you'll see on your Official GMAT won't have these sorts of errors in them.
GMAT assassins aren't born, they're made,
Rich