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Manager
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All the terms of a certain sequence x1,x2,........xnx1,x2,........xn a
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26 Jan 2018, 12:06
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42% (02:05) correct 58% (01:53) wrong based on 36 sessions
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All the terms of a certain sequence x1,x2,........xn are positive integers. The nth term (n>1) of the sequence is given by the formula: xn =xn1 + 1 (If xn1 is even) xn =xn1 + 3 (If xn1 is odd) What is the value of x1 + x6? (1) The second term of the sequence is 3 (2) Two of the first three terms of the sequence are even and add up to 8 == Message from the GMAT Club Team == THERE IS LIKELY A BETTER DISCUSSION OF THIS EXACT QUESTION. This discussion does not meet community quality standards. It has been retired. If you would like to discuss this question please repost it in the respective forum. Thank you! To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative  Verbal Please note  we may remove posts that do not follow our posting guidelines. Thank you.
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Re: All the terms of a certain sequence x1,x2,........xnx1,x2,........xn a
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26 Jan 2018, 13:11
X2 = x1 + 3, x3 = x2+2 = x1+5, x4 = x3+3 = x2 + 4, x5 = x4+1 = x2+5, x6 = x5+3 = x2+8. (1) x2 = 3...x1 = 0, x6 = 11. Works. (2) x1&x2 = even.. Not possible as x2 = x1+odd = odd x2&x3 = even, X2 = 3,x3 = 5..not possible as both not even x3 and x1 not possible as both can't be even at the same time. thus not (2) Sent from my ONEPLUS A5000 using GMAT Club Forum mobile app



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Re: All the terms of a certain sequence x1,x2,........xnx1,x2,........xn a
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27 Jan 2018, 09:57
DTUguy wrote: X2 = x1 + 3, x3 = x2+2 = x1+5, x4 = x3+3 = x2 + 4, x5 = x4+1 = x2+5, x6 = x5+3 = x2+8. (1) x2 = 3...x1 = 0, x6 = 11. Works. (2) x1&x2 = even.. Not possible as x2 = x1+odd = odd x2&x3 = even, X2 = 3,x3 = 5..not possible as both not even x3 and x1 not possible as both can't be even at the same time. thus not (2) Sent from my ONEPLUS A5000 using GMAT Club Forum mobile appI am sorry but it's still not clear to me
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Re: All the terms of a certain sequence x1,x2,........xnx1,x2,........xn a
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27 Jan 2018, 10:10
SandhyAvinash wrote: All the terms of a certain sequence x1,x2,........xn are positive integers. The nth term (n>1) of the sequence is given by the formula:
xn =xn1 + 1 (If xn1 is even)
xn =xn1 + 3 (If xn1 is odd)
What is the value of x1 + x6?
(1) The second term of the sequence is 3
(2) Two of the first three terms of the sequence are even and add up to 8 Odd numbers are being added to \(x_{n1}\), so if \(x_{n1}\) is even then \(x_n\) is odd and if \(x_{n1}\) is odd then \(x_n\) is even to know the value of \(x_1+x_6\) we only need value of \(x_1\) remaining can be found out through the formula given in the question stem Statement 1: implies \(x_2=x_n=3=odd\), so \(x_{n1}=x_1=even\). we can substitute the value of \(x_2\) in the equation \(x_n=x_{n1}+1\) to get \(x_1\). SufficientStatement 2: the sequence will have alternate odd and even numbers, so if out of 1st three two are even, this implies \(x_1\) is even, \(x_2\) is odd and \(x_3\) is even given \(x_1+x_3=8 =>x_1+x_2+3=8\) or \(x_1+x_1+1+3=8\), so \(x_1\) can be calculated. SufficientOption D== Message from the GMAT Club Team == THERE IS LIKELY A BETTER DISCUSSION OF THIS EXACT QUESTION. This discussion does not meet community quality standards. It has been retired. If you would like to discuss this question please repost it in the respective forum. Thank you! To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative  Verbal Please note  we may remove posts that do not follow our posting guidelines. Thank you.




Re: All the terms of a certain sequence x1,x2,........xnx1,x2,........xn a &nbs
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27 Jan 2018, 10:10






