Sequence of Terms

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money9111
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Topic: Sequence of Terms

Wed Feb 03, 2010 11:57 pm

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If the sequence S has 200 terms, what is the 192nd term of S?

1. The first term of S is -40
2. Each term of S after the first term is 3 less than the preceding term.

Data Sufficiency Answers

Did not have a clue how to set this one up.

OA C
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thephoenix
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Thu Feb 04, 2010 12:16 am

money9111 wrote: If the sequence S has 200 terms, what is the 192nd term of S? 1. The first term of S is -40 2. Each term of S after the first term is 3 less than the preceding term. Data Sufficiency Answers Did not have a clue how to set this one up. OA C for nth term of any AP seq formulae is Tn=T1+(n-1)d d is the common diff b/n two succesive terms s1) n=192,t1=-40 but d=? hence insuff s2)n=192,d=-3 but t1=??? hence insuff hence E

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Thu Feb 04, 2010 12:21 am

Moved to "Data Sufficiency" section! Please post the questions in the right folder. Thanks!

ramsharma
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Thu Feb 04, 2010 1:37 am

thephoenix wrote: money9111 wrote: If the sequence S has 200 terms, what is the 192nd term of S? 1. The first term of S is -40 2. Each term of S after the first term is 3 less than the preceding term. Data Sufficiency Answers Did not have a clue how to set this one up. OA C for nth term of any AP seq formulae is Tn=T1+(n-1)d d is the common diff b/n two succesive terms s1) n=192,t1=-40 but d=? hence insuff s2)n=192,d=-3 but t1=??? hence insuff hence E Combine statement 1 and 2(t1 from s1),will get the solution _________________ RAM SHARMA

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sanju09
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Thu Feb 04, 2010 1:50 am

money9111 wrote: If the sequence S has 200 terms, what is the 192nd term of S? 1. The first term of S is -40 2. Each term of S after the first term is 3 less than the preceding term. Data Sufficiency Answers Did not have a clue how to set this one up. OA C GMAT has its favorite few types of sequences to test us on, and the arithmetic progression is one like that. It’s a sequence in which each term except the first is obtained from the previous by adding a constant value, known as the common difference of the arithmetic progression. If a for its first term and d for the common difference, then any nth term to the AP could be found by using a + (n - 1) d formula. Hence, what more we need is a and d. (1) Only a is known as -40. Insufficient (2) This, by definition, only tells the value of d as -3. Insufficient Blended! Done!! C _________________ It takes less time to do something right than to explain why you did it wrong.