Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Re: The product of all the prime numbers less than 20 is closest [#permalink]

Show Tags

02 Jul 2012, 02:17

Hi,

Difficulty level: 650

Product of prime numbers less than 20 = 2*3*5*7*11*13*17*19 =(2*5)*3*(7*13)*(11*17)*19 =3*10*91*189*19 ~(30)*(90*19)*190 ~5700*1710 ~5700*1700 ~9690000 \((=10^6)\)

Thus, Answer is (D)

Regards,

Last edited by cyberjadugar on 02 Jul 2012, 02:39, edited 2 times in total.

Each week we'll be posting several questions from The Official Guide for GMAT® Review, 13th 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: 1. Please provide your solutions to the questions; 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!

The product is \(2*3*5*7*11*13*17*19 = 10 * 21 * 11*(13*17) * 19 \approx10*20*10*15^2*20=900*10^4\approx10^7\).

Therefore, answer C
_________________

PhD in Applied Mathematics Love GMAT Quant questions and running.

Re: The product of all the prime numbers less than 20 is closest [#permalink]

Show Tags

02 Jul 2012, 11:58

2*3*5*7*11*13*17*19 = 210*(10+1)(10+3)(10+7)(10+9) 210 ~ 10*10*2 So the original equation will be equivalent to 10*10*2*(10+1)(10+3)(10+7)(10+9) The highest order of the equation will be 10^6, and other part of expression will not make it closer to 10^7. I have solved it mostly on hunch, no sure how correct I am.

Re: The product of all the prime numbers less than 20 is closest [#permalink]

Show Tags

25 Oct 2013, 03:45

3

This post received KUDOS

1

This post was BOOKMARKED

I have approached in the following way:-

2 x 3 x 5 x 7 x 11 x 13 x 17 x 19 = 10 x 21x 11 x 13 x 17 x 19 = 10 x 10 x 2.1 x 10 x 1.1 x 10 x 1.3 x 10 x 1.7 x 10 x 1.9 = 10^6 x (2.1 x1.1 x 1.3 x 1.7 x 1.9)

The approximation of the (2.1 x 1.7 x 1.9 x 1.3 x 1.1) will be close to 10, so the answer is 10^7

Re: The product of all the prime numbers less than 20 is closest [#permalink]

Show Tags

05 Mar 2014, 10:48

1

This post received KUDOS

Similar to Bunuel's first approach: I thought it was easiest to just do : 2*3*5*7 = 210 11 roughly 10 13 roughly 10 17 roughly 20 19 roughly 20 so 210*10*10*20*20 = 8*10^6 = 10^7

Re: The product of all the prime numbers less than 20 is closest [#permalink]

Show Tags

11 Apr 2014, 18:07

Can anyone comment on my method's effectiveness/efficiency: Prime numbers < 20 are: 2, 3, 5, 7, 11, 13, 17, 19 (Count = 8) Median = 9 (through (7+11)/2) So product should be approx. close to 9^8 which in turn is closest to 10^7, thus answer is 10^7.

Re: The product of all the prime numbers less than 20 is closest [#permalink]

Show Tags

01 Aug 2016, 19:48

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).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

The product of all the prime numbers less than 20 is closest [#permalink]

Show Tags

03 Dec 2016, 18:39

High Quality Question from the Official Set. Its always good to remember the first 10 primes 2 3 5 7 11 13 17 19 23 29

Now the product of all primes <20 => 2*3*5*7*11*13*19 Product => 210*143*323 Approximating => Product =>200*150*300 => 9000000 which is close to 10^7 Hence C _________________

Its been long time coming. I have always been passionate about poetry. It’s my way of expressing my feelings and emotions. And i feel a person can convey...

Written by Scottish historian Niall Ferguson , the book is subtitled “A Financial History of the World”. There is also a long documentary of the same name that the...

Post-MBA I became very intrigued by how senior leaders navigated their career progression. It was also at this time that I realized I learned nothing about this during my...