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# What is the difference between the sixth and the fifth terms

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What is the difference between the sixth and the fifth terms [#permalink]

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20 Dec 2012, 09:02
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What is the difference between the sixth and the fifth terms of the sequence 2, 4, 7, ... whose nth term is n + 2^(n - 1)?

(A) 2
(B) 3
(C) 6
(D) 16
(E) 17
[Reveal] Spoiler: OA

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Re: What is the difference between the sixth and the fifth terms [#permalink]

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20 Dec 2012, 09:04
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What is the difference between the sixth and the fifth terms of the sequence 2, 4, 7, ... whose nth term is n + 2^(n - 1)?

(A) 2
(B) 3
(C) 6
(D) 16
(E) 17

Given that $$a_n=n+2^{n-1}$$, thus:

$$a_6=6+2^{6-1}=38$$;
$$a_5=5+2^{5-1}=21$$;

The difference is 38-21=17.

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Re: What is the difference between the sixth and the fifth terms [#permalink]

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24 Aug 2014, 12:52
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Re: What is the difference between the sixth and the fifth terms [#permalink]

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25 Nov 2014, 14:02
Bunuel wrote:
What is the difference between the sixth and the fifth terms of the sequence 2, 4, 7, ... whose nth term is n + 2^(n - 1)?

(A) 2
(B) 3
(C) 6
(D) 16
(E) 17

Given that $$a_n=n+2^{n-1}$$, thus:

$$a_6=6+2^{6-1}=38$$;
$$a_5=5+2^{5-1}=21$$;

The difference is 38-21=17.

Just one question, why do they mention 2, 4, 7. Is that to throw a test-taker off?
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Re: What is the difference between the sixth and the fifth terms [#permalink]

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26 Nov 2014, 05:10
Bigred2008 wrote:
Bunuel wrote:
What is the difference between the sixth and the fifth terms of the sequence 2, 4, 7, ... whose nth term is n + 2^(n - 1)?

(A) 2
(B) 3
(C) 6
(D) 16
(E) 17

Given that $$a_n=n+2^{n-1}$$, thus:

$$a_6=6+2^{6-1}=38$$;
$$a_5=5+2^{5-1}=21$$;

The difference is 38-21=17.

Just one question, why do they mention 2, 4, 7. Is that to throw a test-taker off?

2, 4, and 7, are the first, second and the third terms of the sequence whose nth term is n + 2^(n - 1). For n = 1, n + 2^(n - 1) = 1 + 2^0 = 2, for n = 2, n + 2^(n - 1) = 2 + 2^1 = 4, and for n = 3, n + 2^(n - 1) = 3 + 2^2 = 7. So, those numbers are given simply as an example.
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Re: What is the difference between the sixth and the fifth terms [#permalink]

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13 Jul 2016, 07:30
What is the difference between the sixth and the fifth terms of the sequence 2, 4, 7, ... whose nth term is n + 2^(n - 1)?

(A) 2
(B) 3
(C) 6
(D) 16
(E) 17

For the sixth term, we need to substitute 6 for n, and for the fifth term, we need to substitute 5 for n. Then we'll find the difference between the two terms.

Let’s first plug 6 in for n.

6 + 2^(6-1)

6 + 2^5

6 + 32 = 38

Next let’s plug 5 in for n.

5 + 2^(5-1)

5 + 2^4

5 + 16 = 21

Thus, the difference between the 6th and 5th term of the sequence is 38 – 21 = 17.

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Re: What is the difference between the sixth and the fifth terms [#permalink]

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31 Jan 2017, 17:37
Plug in 6 and 5 for the sixth and fifth sequence respectively.....

Sixth sequence = 6 + 2^(6-1) = 38

Fifth sequence = 5 + 2^(5-1) = 21

38-21
=
17

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Re: What is the difference between the sixth and the fifth terms [#permalink]

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29 Jun 2017, 19:28
1
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Notice that 2 raised to any positive number will aways be even.

Hence the sixth term will be even+even = even
The fifth term will be odd+even = odd

The only two answers that are odd are B and E. I would say that looking at the sequence we can say that the gap is expanding, hence answer is E
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Re: What is the difference between the sixth and the fifth terms   [#permalink] 29 Jun 2017, 19:28
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