The product of all the prime numbers less than 20 is closest : GMAT Problem Solving (PS)
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 20 Jan 2017, 11:48

GMAT Club Daily Prep

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

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

The product of all the prime numbers less than 20 is closest

Author Message
TAGS:

Hide Tags

Intern
Joined: 07 Dec 2009
Posts: 14
Followers: 0

Kudos [?]: 23 [0], given: 4

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

Show Tags

20 Jan 2010, 05:27
4
This post was
BOOKMARKED
00:00

Difficulty:

75% (hard)

Question Stats:

48% (01:57) correct 52% (01:12) wrong based on 187 sessions

HideShow timer Statistics

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

OPEN DISCUSSION OF THIS QUESTION IS HERE: the-product-of-all-the-prime-numbers-less-than-20-is-closest-135192.html

ALL OG13 QUESTIONS WITH SOLUTIONS ARE HERE: the-official-guide-quantitative-question-directory-143450.html
[Reveal] Spoiler: OA
Manager
Joined: 27 Apr 2008
Posts: 190
Followers: 1

Kudos [?]: 77 [0], given: 1

Show Tags

20 Jan 2010, 07:12
The primes < 20 are 2,3,5,7,11,13,17,19. I would round up/down and estimate using 2,3,5,10,10,10,20,20.

So I have 30x 10^5 = 10^1 x 10^5 = 10^6
Manager
Joined: 17 Jan 2010
Posts: 149
Concentration: General Management, Strategy
GPA: 3.78
WE: Engineering (Manufacturing)
Followers: 1

Kudos [?]: 75 [1] , given: 11

Show Tags

22 Jan 2010, 09:12
1
KUDOS
used the same approach as mr. black but he forgets to use 2s out of last two factors. so it should be 30x4x10^5 = 10^2 x 10^5 = 10^7

IMO the OA is C
Intern
Joined: 15 Mar 2010
Posts: 8
Followers: 1

Kudos [?]: 3 [0], given: 0

Properties of number question from GMAT Review 12th Edition [#permalink]

Show Tags

18 Apr 2010, 22:54
Question 15 on GMAT Review Diagnostic Test

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

The solution in the book makes you CALCULATE the exact number then compare it to the answers, very time consuming without a calculator.

BTW - Are questions in the diagnostic test harder than normal GMAT questions? Or are they the hardest in each category? I find them so much harder than the regular CAT test.

[Reveal] Spoiler:
OA: C
Manager
Joined: 04 Apr 2010
Posts: 89
Schools: UCLA Anderson
Followers: 2

Kudos [?]: 45 [0], given: 17

Re: Properties of number question from GMAT Review 12th Edition [#permalink]

Show Tags

19 Apr 2010, 07:15
If you do the calculation using estimation and rounding, it's actually not too bad.

Yes, there are some difficult questions in the diagnostic test, and they get progressively more difficult throughout the section. They seem to be more "model" GMAT questions than the ones that actually appear on the exam. In order words, they lend themselves to solving easily using methods and tricks. That's not always true on the exam itself.
_________________

Intern
Joined: 08 Apr 2010
Posts: 29
Followers: 1

Kudos [?]: 9 [0], given: 3

Re: Properties of number question from GMAT Review 12th Edition [#permalink]

Show Tags

19 Apr 2010, 22:16
thanatoz wrote:
Question 15 on GMAT Review Diagnostic Test

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

The solution in the book makes you CALCULATE the exact number then compare it to the answers, very time consuming without a calculator.

BTW - Are questions in the diagnostic test harder than normal GMAT questions? Or are they the hardest in each category? I find them so much harder than the regular CAT test.

[Reveal] Spoiler:
OA: C

this one can be done easily as shown below.
the prime numbers <20 are 2,3,5,7,11,13,17,19
taking the product of two at a time, we get 6, 35, 77, 221 and 19
on further applying this method of rounding and approximating, we see that the product nears 10^7
_________________

CHEERS
fivezero7

Current Student
Joined: 06 Sep 2013
Posts: 2035
Concentration: Finance
GMAT 1: 770 Q0 V
Followers: 62

Kudos [?]: 594 [0], given: 355

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

Show Tags

26 Sep 2013, 06:54
melissawlim wrote:
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

Official Guide 12 Question

 Question: 15 Page: 22 Difficulty: 700

Find All Official Guide Questions

Video Explanations:

Hi Bunnuel,

Any thoughts on this one?

Cheers!
Math Expert
Joined: 02 Sep 2009
Posts: 36582
Followers: 7086

Kudos [?]: 93274 [0], given: 10555

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

Show Tags

26 Sep 2013, 07:17
jlgdr wrote:
melissawlim wrote:
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

Official Guide 12 Question

 Question: 15 Page: 22 Difficulty: 700

Find All Official Guide Questions

Video Explanations:

Hi Bunnuel,

Any thoughts on this one?

Cheers!

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

We should find the approximate value of 2*3*5*7*11*13*17*19 to some power of 10.

# of different approximations are possible.

Approach #1:

2*5=10;
3*7=~20 (actually more than 20);
11*19=~200 (actually more than 200);
13*17=~200 (actually more than 200);

$$2*3*5*7*11*13*17*19\approx{10*20*200*200=8*10^6}\approx{10^7}$$.

Approach #2:

2*5=10
3*17=~50 (actually more than 50);
7*13=~100 (actually less than 100);
11*19=~200 (actually more than 200)

$$2*3*5*7*11*13*17*19\approx{10*50*100*200}=10^7$$.

OPEN DISCUSSION OF THIS QUESTION IS HERE: the-product-of-all-the-prime-numbers-less-than-20-is-closest-135192.html

ALL OG13 QUESTIONS WITH SOLUTIONS ARE HERE: the-official-guide-quantitative-question-directory-143450.html

_________________
Re: The product of all the prime numbers less than 20 is closest   [#permalink] 26 Sep 2013, 07:17
Similar topics Replies Last post
Similar
Topics:
21 The product of all the prime numbers less than 20 is closest 10 26 Jan 2012, 09:29
7 The product of all the prime numbers less than 20 is closest to which 3 03 Jun 2011, 09:43
9 The product of all the prime numbers less than 20 is closest to which 9 07 Dec 2010, 19:24
9 The product of all the prime numbers less than 20 is closest to which 7 26 Nov 2010, 07:20
5 The product of all the prime numbers less than 20 is closest to which 6 12 Jun 2009, 20:28
Display posts from previous: Sort by