The product of the Â…5 smallest two-digit prime numbers 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
any shortcut method?
the product of 5 smallest prime numbers
This topic has expert replies
-
- Master | Next Rank: 500 Posts
- Posts: 226
- Joined: Thu Nov 25, 2010 12:19 am
- Thanked: 3 times
- Followed by:2 members
Last edited by nafiul9090 on Wed Jul 04, 2012 4:46 pm, edited 1 time in total.
-
- Senior | Next Rank: 100 Posts
- Posts: 90
- Joined: Wed Mar 21, 2012 1:27 am
- Thanked: 5 times
- Followed by:2 members
- eagleeye
- Legendary Member
- Posts: 520
- Joined: Sat Apr 28, 2012 9:12 pm
- Thanked: 339 times
- Followed by:49 members
- GMAT Score:770
The smallest two digit primes are 11, 13, 17, 19 and 23.
So their product = 11*13*17*19*23.
To approximate, put them in pairs. 11*19*13*17*23
11*19 is approx 10*20 = 200
13*17 is approx 10*20 = 200
23 is approx 25
multiplying 200*200*25 = 10^6.
So it is closest to 10^6.
Let me know if this helps
So their product = 11*13*17*19*23.
To approximate, put them in pairs. 11*19*13*17*23
11*19 is approx 10*20 = 200
13*17 is approx 10*20 = 200
23 is approx 25
multiplying 200*200*25 = 10^6.
So it is closest to 10^6.
Let me know if this helps
- Bill@VeritasPrep
- GMAT Instructor
- Posts: 1248
- Joined: Thu Mar 29, 2012 2:57 pm
- Location: Everywhere
- Thanked: 503 times
- Followed by:192 members
- GMAT Score:780
Grouping and estimating is a great way to go, especially when the answers are so spread out.eagleeye wrote:The smallest two digit primes are 11, 13, 17, 19 and 23.
So their product = 11*13*17*19*23.
To approximate, put them in pairs. 11*19*13*17*23
11*19 is approx 10*20 = 200
13*17 is approx 10*20 = 200
23 is approx 25
multiplying 200*200*25 = 10^6.
So it is closest to 10^6.
Let me know if this helps
Join Veritas Prep's 2010 Instructor of the Year, Matt Douglas for GMATT Mondays
Visit the Veritas Prep Blog
Try the FREE Veritas Prep Practice Test
Visit the Veritas Prep Blog
Try the FREE Veritas Prep Practice Test
GMAT/MBA Expert
- Scott@TargetTestPrep
- GMAT Instructor
- Posts: 7249
- Joined: Sat Apr 25, 2015 10:56 am
- Location: Los Angeles, CA
- Thanked: 43 times
- Followed by:29 members
The product of the 5 smallest two-digit primes is 11 x 13 x 17 x 19 x 23, which we can approximate as the product 10 x 10 x 20 x 20 x 20 = 800,000. We see that this is closest to 1,000,000, or 10^6.nafiul9090 wrote:The product of the Â…5 smallest two-digit prime numbers 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
Answer: D
Scott Woodbury-Stewart
Founder and CEO
[email protected]
See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews