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What is the average of the first 20 positive integers?

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Sajjad1994
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What is the average of the first 20 positive integers? [#permalink] New post   12 Mar 2020, 06:01
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A
B
C
D
E

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5% (low)

Question Stats:

90% (00:42) correct 10% (01:34) wrong based on 39 sessions
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What is the average of the first 20 positive integers?

(A) 7\(\frac{1}{2}\)

(B) 10

(C) 10\(\frac{1}{2}\)

(D) 15

(E) 20
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C
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BrentGMATPrepNow
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What is the average of the first 20 positive integers? [#permalink] New post   12 Mar 2020, 06:05
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SajjadAhmad wrote:
What is the average of the first 20 positive integers?

(A) 7\(\frac{1}{2}\)

(B) 10

(C) 10\(\frac{1}{2}\)

(D) 15

(E) 20


Key property: If a set of numbers are equally spaced, and the average of all of the numbers equals the average of the greatest and least values.

We want: 1 + 2 + 3 + 4 + ... + 18 + 19 + 20

So, when we apply the above property, the average of all 20 integers = (1 + 20)/2 = 21/2 = 10.5

Answer: C

Cheers,
Brent
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Re: What is the average of the first 20 positive integers? [#permalink] New post   15 Mar 2020, 04:43
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SajjadAhmad wrote:
What is the average of the first 20 positive integers?

(A) 7\(\frac{1}{2}\)

(B) 10

(C) 10\(\frac{1}{2}\)

(D) 15

(E) 20


The average of the first 20 positive integers is (20 + 1)/2 = 21/2 = 10.5.

Answer: C
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fireagablast
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Re: What is the average of the first 20 positive integers? [#permalink] New post   21 Mar 2020, 19:13
why is this labeled a 600-700 problem..
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Re: What is the average of the first 20 positive integers? [#permalink] New post   21 Mar 2020, 21:41
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fireagablast wrote:
why is this labeled a 600-700 problem..


This is newly posted question so tag may or may not resembles the real difficulty level initially, after a few more timer attempts system will set the difficulty level tag automatically.

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Re: What is the average of the first 20 positive integers? [#permalink]
21 Mar 2020, 21:41
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