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The proceeding list of terms is an arithmetic sequence. How many terms

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The proceeding list of terms is an arithmetic sequence. How many terms [#permalink]

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The proceeding list of terms is an arithmetic sequence. How many terms are included in the list?

2, \(a_2\), ..., 247

(1) \(a_n=5n-3\)
(2) \(a_2=7\)
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Re: The proceeding list of terms is an arithmetic sequence. How many terms [#permalink]

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samuelz wrote:
The proceeding list of terms is an arithmetic sequence. How many terms are included in the list?
2,\(a_2\),...,247

1)\(a_n\)=5n-3
2)\(a_2\)=7


2, a2, ......,247

stmt-1:
an = 5n - 3
a2 = 5*2 - 3 = 7

notice that the given sequence is arithmatic. it means the difference between the terms will be same i.e. a2 - a1 = 7-2 = 5. Knowing this difference and as first and last term is given you can find the number of terms in sequence.
Sufficient

stmt-2:
same as stmt-1. you get to know the value of a2 and hence the difference between terms.
sufficient.

Answer D

What is the source of this question?
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Re: The proceeding list of terms is an arithmetic sequence. How many terms [#permalink]

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New post 02 Apr 2017, 07:11
Thanks a lot for the explanation. I've found this question in McGraw-Hill Gmat Prep books.

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Re: The proceeding list of terms is an arithmetic sequence. How many terms [#permalink]

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New post 03 Apr 2017, 14:50
Hello,
FOR
(1) I tried 247=5n-3, which got me n=244/5, How should I interpret this result?
What am I doing wrong?

Thanks,

Miral

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Re: The proceeding list of terms is an arithmetic sequence. How many terms [#permalink]

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Re: The proceeding list of terms is an arithmetic sequence. How many terms [#permalink]

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New post 01 Nov 2017, 11:15
Hi Bunuel,
I have one question, does arithmetic sequence necessarily mean arithmetic progression?

Statement 1: sufficient and substituting the value for n, we find the sequence is actually arithmetic progression.

Statement 2: can there be any sequence whose equation, gives 2, 7,.....247, ? may be or may be not, accordingly number of terms in the list will vary.

So confused between A and D

Can you please help?

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Re: The proceeding list of terms is an arithmetic sequence. How many terms [#permalink]

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New post 01 Nov 2017, 12:13
hellosanthosh2k2 wrote:
Hi Bunuel,
I have one question, does arithmetic sequence necessarily mean arithmetic progression?

Statement 1: sufficient and substituting the value for n, we find the sequence is actually arithmetic progression.

Statement 2: can there be any sequence whose equation, gives 2, 7,.....247, ? may be or may be not, accordingly number of terms in the list will vary.

So confused between A and D

Can you please help?


there can be less or more terms in the sequence 2, 7,... 247 BUT because the question stamp states that "The proceeding list of terms is an arithmetic sequence", the number of terms are fixed!

and yes - arithmatic sequence means arithmatic progression.
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Re: The proceeding list of terms is an arithmetic sequence. How many terms [#permalink]

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New post 01 Nov 2017, 18:51
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Because we already know that "the proceeding list of terms is an arithmetic sequence" and that the value of the first and the last term, we can calculate the number of terms in the list when we know the difference between 2 consecutive terms.

(1) a(n)=5n−3 => a2 = 10 - 3 =7 => a2 - a1 = 5 => sufficient.

(2) a2=7 => same as (1)

Hence, the answer is D

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Re: The proceeding list of terms is an arithmetic sequence. How many terms   [#permalink] 01 Nov 2017, 18:51
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