Hi,
I have a question in regards to Official Guide 13
Data Sufficiency questions 67 and 163.
I chose d for both questions but for question
67, d was incorrect because the quadratic allowed
For two possible answer choices,but for question 167 the correct
approach is to drop the negative quadratic (-10)
and leave the positive 15. If so why couldn't the same be done
for question 67. They are both value DS questions
regarding quadractics.
I'm not sure if I am allowed to post the questions, so I will not.
Any help will be greatly appreciated.
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Official Guide DS #163
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theCodeToGMAT
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ceilidh.erickson
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Hi Nadia,
The OG is copyrighted material, but I think you'll find that you won't get in trouble for posting the actual question.
Rahul, you're right that generally people should post one comment per thread, but I think it's certainly reasonable to compare two similar questions, and ask what distinguishes them.
The biggest distinction between #67 and #163 is that 163 has an POSITIVE CONSTRAINT, and 67 does not.
#67: "What is the value of integer n?"
Here, n can be any integer, positive of negative - there's no restriction. When given n(n + 1) = 6, n could equal 2 or -3, and the statement is thus insufficient.
#163 "How many members does the club have?"
When you're dealing with a word problem that involves real-life, countable objects (people, books, cars, etc), there is an implied POSITIVE CONSTRAINT. We can't have a negative number of people! Thus, when the quadratic gives us -10 or 15, we know that the number of members cannot be negative, so it must be 15.
The OG is copyrighted material, but I think you'll find that you won't get in trouble for posting the actual question.
Rahul, you're right that generally people should post one comment per thread, but I think it's certainly reasonable to compare two similar questions, and ask what distinguishes them.
The biggest distinction between #67 and #163 is that 163 has an POSITIVE CONSTRAINT, and 67 does not.
#67: "What is the value of integer n?"
Here, n can be any integer, positive of negative - there's no restriction. When given n(n + 1) = 6, n could equal 2 or -3, and the statement is thus insufficient.
#163 "How many members does the club have?"
When you're dealing with a word problem that involves real-life, countable objects (people, books, cars, etc), there is an implied POSITIVE CONSTRAINT. We can't have a negative number of people! Thus, when the quadratic gives us -10 or 15, we know that the number of members cannot be negative, so it must be 15.
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
