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# product of prime numbers

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Intern
Joined: 08 Jun 2009
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product of prime numbers [#permalink]  12 Jun 2009, 20:28
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Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 100% (00:00) wrong based on 2 sessions
Is there any quick way to solve this question?

The product of all the prime numbers less than 20 is closest to which of the following powers of 10?

(A) 10^9
(B) 10^8
(C) 10^7
(D) 10^6
(E) 10^5

[Reveal] Spoiler:
OA is C
Founder
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Location: United States (WA)
GMAT 1: 750 Q49 V42
GPA: 3.5
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Kudos [?]: 13568 [0], given: 3865

Re: product of prime numbers [#permalink]  12 Jun 2009, 23:12
Expert's post
Welcome to GMAT Club Jozu!

There is a neater way to post questions. You can learn how to post math symbols here: writing-mathematical-symbols-in-posts-72468.html. Usually, all you have to do is to highlight the text and hit the M button. Bu there are exceptions such as fractions.

You can also hide the Original Answer using the "Spoiler" functionality. I added it to your post. Here is the original question rewritten:

The product of all the prime numbers less than 20 is closest to which of the following powers of 10?

(A) $$10^9$$
(B) $$10^8$$
(C) $$10^7$$
(D) $$10^6$$
(E) $$10^5$$
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Senior Manager
Joined: 08 Jan 2009
Posts: 329
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Kudos [?]: 91 [0], given: 5

Re: product of prime numbers [#permalink]  13 Jun 2009, 02:26
i found this method in another forum. thought i could share it with u.

2*3*5*7*11*13*17*19

7*11*13 2*5 17*19 * 3

1001 * 10 * (18-1))(18+1) 3

approximately 10^4 *(324-1) *3

10^4 * 323*3

9690000

nearest power 10 is 10^7
Manager
Joined: 04 Sep 2010
Posts: 84
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Kudos [?]: 5 [0], given: 11

Re: product of prime numbers [#permalink]  16 Jun 2011, 20:45
how to solve this question using approximation method?
Re: product of prime numbers   [#permalink] 16 Jun 2011, 20:45
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