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# There is an arithmetic sequence An where n is a positive integer such

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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
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GMAT 1: 760 Q51 V42
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There is an arithmetic sequence An where n is a positive integer such  [#permalink]

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08 Nov 2016, 02:15
00:00

Difficulty:

55% (hard)

Question Stats:

56% (01:41) correct 44% (02:08) wrong based on 128 sessions

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There is an arithmetic sequence An where n is a positive integer such that $$A_{n+1}=A_n+3$$, what is the value of A10?

1) A1=3.
2) A3+A6=27

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"Only $79 for 1 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 8027 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: There is an arithmetic sequence An where n is a positive integer such [#permalink] ### Show Tags 10 Nov 2016, 01:17 ==>In the original condition, there are 2 variables (An+1, An), and 1 equation (An+1=An+3), so D is highly likely to be the answer. 1)=2), so you get A10=30, hence unique, and sufficient. The answer is D. Answer: D _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$79 for 1 month Online Course"
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Re: There is an arithmetic sequence An where n is a positive integer such  [#permalink]

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10 Nov 2016, 03:11
An+1=An+3. Difference between terms is 3.
nth term an arithmetic sequence, $$An = A1 + (n-1)*D$$
An = A1 + (n-1)*3
$$A10 = A1 + 9 *3$$
To find A10, it is sufficient to find A1

1) A1=3.

A1 is known, hence sufficient.

2) A3+A6=27
A1+ (2-1)*3 + A1 + (6-1)*3 = 27
2A1 = 9
A1 = 4.5
Hence sufficient.

Each statement alone is sufficient. Option D
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Re: There is an arithmetic sequence An where n is a positive integer such  [#permalink]

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13 Nov 2016, 22:49
1
Please use mathematical indentation. The question becomes unclear otherwise.
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Joined: 05 Dec 2015
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Re: There is an arithmetic sequence An where n is a positive integer such  [#permalink]

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07 Jan 2017, 23:41
great post - do you mind elaborating on how you got the difference between terms being 3?

rudra316 wrote:
An+1=An+3. Difference between terms is 3.
nth term an arithmetic sequence, $$An = A1 + (n-1)*D$$
An = A1 + (n-1)*3
$$A10 = A1 + 9 *3$$
To find A10, it is sufficient to find A1

1) A1=3.

A1 is known, hence sufficient.

2) A3+A6=27
A1+ (2-1)*3 + A1 + (6-1)*3 = 27
2A1 = 9
A1 = 4.5
Hence sufficient.

Each statement alone is sufficient. Option D
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Posts: 8006
Re: There is an arithmetic sequence An where n is a positive integer such  [#permalink]

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08 Jan 2017, 00:00
2
mdacosta wrote:
great post - do you mind elaborating on how you got the difference between terms being 3?

rudra316 wrote:
An+1=An+3. Difference between terms is 3.
nth term an arithmetic sequence, $$An = A1 + (n-1)*D$$
An = A1 + (n-1)*3
[

Hi,

The Q is complicated because the author has not used mathematical notations and has left each one to think their own way..
$$A_{n+1}=A_n+3$$...
So (n+1) th term is 3 more than the nth term.

We have to find $$A_10$$...
From the equation $$A_{n+1}=A_n+3$$, we know that each term is related to every other term
Thus web just require to know any term.

Both statements give us a value and a variable, so both will give us a answer..
Suff

D
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Re: There is an arithmetic sequence An where n is a positive integer such  [#permalink]

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08 Jan 2017, 00:16
Thanks chetan !! Those notations ate my time..
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Re: There is an arithmetic sequence An where n is a positive integer such  [#permalink]

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20 Feb 2018, 11:18
1
MathRevolution wrote:
There is an arithmetic sequence An where n is a positive integer such that An+1=An+3, what is the value of A10?

1) A1=3.
2) A3+A6=27

Very Poor way of writing the question, Moderator should edit the question so that it appears in the correct format.
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Re: There is an arithmetic sequence An where n is a positive integer such   [#permalink] 20 Feb 2018, 11:18
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