Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

For a finite sequence of nonzero numbers, the number of [#permalink]

Show Tags

23 May 2008, 13:02

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

For a finite sequence of nonzero numbers, the number of variations in sign is defined as the number of pairs of consecutive terms of the sequence for which the product of the two consecutive terms is negative. What is the number of variations in sign for the sequence 1, -3, 2, 5, -4, -6?

YihWei, that is the correct answer...I got this simple one wrong because I ordered the set...why would one not order the set in this case? How would you reword this question if they DID want you to order the set?

YihWei, that is the correct answer...I got this simple one wrong because I ordered the set...why would one not order the set in this case? How would you reword this question if they DID want you to order the set?

I didn't order the set because the question didn't ask me to do that. I just try to "play dumb" and do exactly what the question asks me to do and nothing more. If they did want us to order the set I would probably just add a statement to the end of the question saying, "Put the sequence in ascending/descending order prior to solving the question". I think this is just a simple case of you overthinking the question. Stop being smarter than the GMAT
_________________

Because this is NOT a set... it clearly states SEQUENCE. There are either Finite or Infinite sequences. In this case it was Finite so there is a set number of values.

YihWei, that is the correct answer...I got this simple one wrong because I ordered the set...why would one not order the set in this case? How would you reword this question if they DID want you to order the set?

Ive been stumped on this question for soo long (I just memorized the answer and somehow convinced myself that the answer is 3 and not 1) - I did the same thing you did.

Or just think about what they are asking for in common sense terms. The "number of variations in sign" is how many times the sequence flips between positive and negative numbers. So it starts positive at 1, then flips once at -3, then flips a second time at 2, then stays the same at 5, then flips a third time at -4, then stays the same at -6. You could get the answer without even looking at the numerals, just the signs. +-++-- = 3 flips.

Or just think about what they are asking for in common sense terms. The "number of variations in sign" is how many times the sequence flips between positive and negative numbers. So it starts positive at 1, then flips once at -3, then flips a second time at 2, then stays the same at 5, then flips a third time at -4, then stays the same at -6. You could get the answer without even looking at the numerals, just the signs. +-++-- = 3 flips.

nice way of doing this..but i gurantee on exam day under the stress from the exam..one will most likely get this wrong cause they will most likely over look one of the - signs or + signs..and under pressure to hurry will make a careless mistake..

YihWei, that is the correct answer...I got this simple one wrong because I ordered the set...why would one not order the set in this case? How would you reword this question if they DID want you to order the set?

Jimmy I did the same things as well, I ordered the sequence which screwed me!

A few takeaways from this problem:

1). Dont assume anything, in this case the assumption made was to order the sequence in ascending order when not explicitly told to do so 2). Pay attention to Detail - As chengliu pointed out, this is NOT a set, rather a sequence, so I can see how ordering the set might make sense in that case, but once again something should state/trigger that action. (For this problem, "consecutive" was the keyword that screwed me. In a set consecutive numbers means they are either ordered in ascending/descending order. However in a sequence, depending on the sequence pattern - consecutive numbers are NOT necessarily ordered in ascending/descending order.