While solving GMAT quant questions, always remember that your one goal is to identify the correct answer as efficiently as possible, and not to please your former math teachers.
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Comment on Recursive Definitions of Terms
https://gmatclub.com/forum/in
If we start from back
t11/t8 = t10*2^11
= t9*2^10*2^11
= t8*2^10*2^11*2^9
= t7*2^30*2^8/t7*2^8
= 2^30
Question link: https:/
Question link: https://gmatclub.com/forum/in-a-certain-sequence-term1-64-and-for-all-26...
Nice!
What is the best way to
A quick/easy way to identify
A quick/easy way to identify a recursive sequence is to try finding the value of a random term.
For example, it you try to find the value of term_10, and you discover that, in order to find term_10, you must first find the value of term_9, then you're dealing with a recursive sequence.
Does that help?
Cheers,
Brent
Hi Brent,
Doubt regarding this question: <https://gmatclub.com/forum/in-the-sequence-s-of-numbers-each-term-after-the-first-two-terms-is-167947.html>
It is clear that Statement 1 is SUFF, however I also find Statement 2 SUFF, since I could rephrase the target question transforming S5 to an equation involving S1. Hence, Statement2 is : whateverquestioninvolvingS1 = 21.
May you help me? Cheers.
Question link: https:/
Question link: https://gmatclub.com/forum/in-the-sequence-s-of-numbers-each-term-after-...
Sorry, I'm not sure what you mean by "rephrase the target question transforming S5 to an equation involving S1.Hence, Statement2 is : whateverquestioninvolvingS1 = 21." San you please elaborate on this approach?
-----------------------------
In the meantime....
TARGET QUESTION: What is the value of term5?
Statement 2 tells us that term6 + term7 = 21.
To show that Statement 2 is not sufficient, consider these two conflicting cases:
CASE i: term6 = 10 and term7 = 11
Since we know that term7 = term5 + term6, we can write: 11 = term5 + 10
So, in this case, term5 = 1
CASE ii: term6 = 9 and term7 = 12
Since we know that term7 = term5 + term6, we can write: 12 = term5 + 9
So, in this case, term5 = 3
Since we can't answer the target question with certainty, statement 2 is not sufficient.
Does that help?
Totally. Thanks for answering