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# In a certain sequence, the term

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CEO
Joined: 11 Sep 2015
Posts: 3447
In a certain sequence, the term  [#permalink]

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26 Oct 2016, 11:52
Top Contributor
00:00

Difficulty:

15% (low)

Question Stats:

79% (01:38) correct 21% (01:25) wrong based on 89 sessions

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In a certain sequence, every term, tn, is given by the formula tn = (k)(n) + 15, for some constant k and for all n > 1. What is the value of t10?

(1) t8 - t7 = 5
(2) (t8)/(t7) = 11/10

*Kudos for all correct solutions

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Manager
Joined: 05 Jun 2015
Posts: 82
Location: United States
WE: Engineering (Transportation)
Re: In a certain sequence, the term  [#permalink]

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26 Oct 2016, 17:13
3
To find the 10th term, we need to know the value of k. It is sufficient to check whether we can find the value of k from the two options

(1) $$t8 - t7 = 5$$
$$8K+15 -(7K+15)= 15$$
k = 5

(1) is Sufficient

(2) (t8)/(t7) = 11/10
$$\frac{8k+15}{7k+15} = \frac{11}{10}$$
this is a linear equation in k, k can be found out.

(2) is also sufficient.

Hence Option D
Manager
Joined: 29 Aug 2008
Posts: 110
Re: In a certain sequence, the term  [#permalink]

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26 Oct 2016, 21:55
1
tn = K(n) + 15

t10 = ?

Statement 1 = 8k + 15 - 7k - 15 = 5, we can solve for x and find t10. Sufficient.

Statement 2 = (8k + 15)/(7k + 15) = 11/10, single variable equation, we can solve for K and find t10, Sufficient.

Option D.
Intern
Joined: 20 Aug 2014
Posts: 3
Re: In a certain sequence, the term  [#permalink]

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31 Oct 2016, 04:10
1
t10=10k+15

So, value of k required. k=??

(1) t8−t7=5

8K+15−(7K+15)=5
k = 5

(1) is Suff

A or D

(2) (t8)/(t7) = 11/10
8k+15/7k+15=11/10

From here, k can be found.

(2) is also Suff

Option D
Intern
Status: GMAT_BOOOOOOM.............. Failure is not an Option
Joined: 22 Jul 2013
Posts: 11
Location: India
Concentration: Strategy, General Management
GMAT 1: 510 Q38 V22
GPA: 3.5
WE: Information Technology (Consulting)
Re: In a certain sequence, the term  [#permalink]

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24 Nov 2016, 02:40
Based on the given formula :tn = (k)(n) + 15

Find out t10 It means t10 = 10K + 5 . So if we are able to find K then t10 can be found.

Statement 1 : t8−t7=5
==> 8k +15 - 7k -15 = 5
K = 5 Hence Sufficient

Statement 2 : (t8)/(t7) = 11/10

(8k+15)/ (7k+15) = 11/10

Cross multiply and get the value of the K .Hence Sufficient .

Kudos will be appreciated if it was helpful.
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Joined: 09 Sep 2013
Posts: 9892
Re: In a certain sequence, the term  [#permalink]

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20 Oct 2018, 06:28
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: In a certain sequence, the term   [#permalink] 20 Oct 2018, 06:28
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