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The sequence x1, x2, ... xn is such that x1 = 5, x2 = ­5, x3 = 0, x4 =

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Joined: 07 Jun 2017
Posts: 174
Location: India
Concentration: Technology, General Management
GMAT 1: 660 Q46 V38
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WE: Information Technology (Computer Software)
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The sequence x1, x2, ... xn is such that x1 = 5, x2 = ­5, x3 = 0, x4 =  [#permalink]

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New post Updated on: 19 Feb 2018, 05:58
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32% (01:48) correct 68% (02:29) wrong based on 40 sessions

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The sequence \(x_1\), \(x_2\), ..., \(x_n\) is such that \(x_1 = 5\), \(x_2 = -­5\), \(x_3 = 0\), \(x_4 = ­- 2\), \(x_5 = 4\) and \(x_n =x_{ n­-5}\). P is an integer greater than 5. P = ?

(1) Sum of the first P terms in the given sequence is 10.
(2) Sum of the first P + 3 terms in the given sequence is 10.

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email: nkmungila@gmail.com
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Originally posted by nkmungila on 25 Oct 2017, 23:28.
Last edited by Bunuel on 19 Feb 2018, 05:58, edited 1 time in total.
Renamed the topic and edited the question.
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Re: The sequence x1, x2, ... xn is such that x1 = 5, x2 = ­5, x3 = 0, x4 =  [#permalink]

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New post 26 Oct 2017, 02:42
nkmungila wrote:
The sequence \(X1, X2....Xn\) is such that \(X1 = 5, X2 = -­5, X3 = 0, X4 = ­- 2, X5 = 4\) and \(X n = X n­-5\). P is an integer greater than 5. P=?

(1) Sum of the first P terms in the given sequence is 10.
(2) Sum of the first P+3 terms in the given sequence is 10.



Hi..

I am sure the \(X n = X n­-5\) actually means \(X_n = X_{n­-5}\)
so the sequence is ..
\(5,-5,0,-2,4,5,-5,0,-2,4.........\)

lets see the statements...
(1) Sum of the first P terms in the given sequence is 10.
lets see how the SUM increases...
5+(-5)=0....0+0=0.....0+(-2)=-2....-2+4=2.....2+5=7.....7_5=2
so if we are looking at SUM as 10, there should be 5 repetitions as EACH repetition gives us 2...
so 25 numbers in sequence will have 10 as SUM
But when we add 5 and -5 are added, SUM will again be 10 and then when we add 0(28th number), Sum will again be 10
so ANS can be 25, 27 or 28
Insuff

(2) Sum of the first P+3 terms in the given sequence is 10.
As in statement I, P+3 could be 25,27 or 28
Insuff

combined..
P can be 25, 27 or 28
if P is 25, P + 3 =28......POSSIBLE
if P =27, P+3=30....NO
if P+28, P+3=31...NO

so P = 25
sufficient

C
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1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html


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Re: The sequence x1, x2, ... xn is such that x1 = 5, x2 = ­5, x3 = 0, x4 = &nbs [#permalink] 26 Oct 2017, 02:42
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