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# If there are 664,579 prime numbers among the first 10 millio

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Math Expert
Joined: 02 Sep 2009
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If there are 664,579 prime numbers among the first 10 millio [#permalink]

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26 Dec 2013, 09:02
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25% (medium)

Question Stats:

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The Official Guide For GMAT® Quantitative Review, 2ND Edition

If there are 664,579 prime numbers among the first 10 million positive integers, approximately what percent of the first 10 million positive integers are prime numbers?

(A) 0.0066%
(B) 0.066%
(C) 0.66%
(D) 6.6%
(E) 66%

Problem Solving
Question: 10
Category: Arithmetic Percents
Page: 63
Difficulty: 550

GMAT Club is introducing a new project: The Official Guide For GMAT® Quantitative Review, 2ND Edition - Quantitative Questions Project

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[Reveal] Spoiler: OA

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Math Expert
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Re: If there are 664,579 prime numbers among the first 10 millio [#permalink]

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26 Dec 2013, 09:02
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SOLUTION

If there are 664,579 prime numbers among the first 10 million positive integers, approximately what percent of the first 10 million positive integers are prime numbers?

(A) 0.0066%
(B) 0.066%
(C) 0.66%
(D) 6.6%
(E) 66%

We need to find 664,579 is what percent of 10 million: $$\frac{664,579}{10,000,000}*100\approx{6.6%}$$.

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Re: If there are 664,579 prime numbers among the first 10 millio [#permalink]

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26 Dec 2013, 21:00
2
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664579=x/100 * 10,000,000 = approx. 6.6%

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Manager
Status: GMATting
Joined: 21 Mar 2011
Posts: 106
Concentration: Strategy, Technology
GMAT 1: 590 Q45 V27
Re: If there are 664,579 prime numbers among the first 10 millio [#permalink]

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26 Dec 2013, 22:50
1
KUDOS
664,579 = (x/100) * 10^7;
664, 579 = x * 10^5
=> x = 664, 579/10^5 = 6.64579 ~ 6.6%

Ans is (D).
Manager
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Location: India
GMAT Date: 05-23-2015
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Re: If there are 664,579 prime numbers among the first 10 millio [#permalink]

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27 Dec 2013, 01:37
2
KUDOS
Writing$$664,579$$ as $$0.66 * 10^6$$
Percentage of prime numbers in 10 million numbers $$= ( (0.66 * 10^6)/(10*10^6))* 100=6.6%$$

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Posts: 704
Location: India
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Re: If there are 664,579 prime numbers among the first 10 millio [#permalink]

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30 Dec 2013, 05:14
If there are 664,579 prime numbers among the first 10 million positive integers, approximately what percent of the first 10 million positive integers are prime numbers?

(A) 0.0066%
(B) 0.066%
(C) 0.66%
(D) 6.6%
(E) 66%

Sol: Given there 664 579 prime nos in first 10 million positive integers.So % will be

(0.664579*10^6/10 *10^6)*100 ------> 0.664579*10 and thus 6.6%
Ans D
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Manager
Joined: 20 Dec 2013
Posts: 124
Re: If there are 664,579 prime numbers among the first 10 millio [#permalink]

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02 Jan 2014, 05:56
10 million is 10 x 10^6 = 10^7

(664 579/10^7) x 10^2 = 6.6 %

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Joined: 21 Oct 2013
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Location: Germany
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Re: If there are 664,579 prime numbers among the first 10 millio [#permalink]

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27 Aug 2014, 03:49
100,000 is 1 % of 10,000,000 hence 664,579 will be approx. 6.6% of 10,000,000.
Intern
Joined: 24 Mar 2015
Posts: 3
Re: If there are 664,579 prime numbers among the first 10 millio [#permalink]

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31 Mar 2015, 06:56
664,579 / 10,000,000 *100 =x%

you can reduce the 10 million by 100, so that you only have 100,000 in the denominator. Now, bot the nominator and denominator have the same amount of digits and from this point you can ask yourself how much for e.g. 664/100 is. The solution is 6,64 or in this case 6,6%
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Posts: 1889
Re: If there are 664,579 prime numbers among the first 10 millio [#permalink]

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31 Mar 2015, 11:24
Bunuel wrote:
The Official Guide For GMAT® Quantitative Review, 2ND Edition

If there are 664,579 prime numbers among the first 10 million positive integers, approximately what percent of the first 10 million positive integers are prime numbers?

(A) 0.0066%
(B) 0.066%
(C) 0.66%
(D) 6.6%
(E) 66%

Problem Solving
Question: 10
Category: Arithmetic Percents
Page: 63
Difficulty: 550

GMAT Club is introducing a new project: The Official Guide For GMAT® Quantitative Review, 2ND Edition - Quantitative Questions Project

Each week we'll be posting several questions from The Official Guide For GMAT® Quantitative Review, 2ND Edition and then after couple of days we'll provide Official Answer (OA) to them along with a slution.

We'll be glad if you participate in development of this project:
2. Please vote for the best solutions by pressing Kudos button;
3. Please vote for the questions themselves by pressing Kudos button;
4. Please share your views on difficulty level of the questions, so that we have most precise evaluation.

Thank you!

664579/10 million
= 664579/100,000,00
= 0.066
= 0.066 * 100%
= 6.6%

Hence option (D).

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Intern
Joined: 11 Nov 2015
Posts: 1
Re: If there are 664,579 prime numbers among the first 10 millio [#permalink]

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11 Nov 2015, 14:11
You can find interesting facts and puzzles about Prime Numbers and Magic Squares, Smith Numbers, and Arithmetic and Palindromic Primes on Glenn Westmore's blog.
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Posts: 6644
Re: If there are 664,579 prime numbers among the first 10 millio [#permalink]

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12 Nov 2017, 23:20
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Re: If there are 664,579 prime numbers among the first 10 millio   [#permalink] 12 Nov 2017, 23:20
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