Author 
Message 
TAGS:

Hide Tags

Manager
Joined: 20 Oct 2013
Posts: 63

Re: For every positive even integer n, the function h(n) is defined to be [#permalink]
Show Tags
04 May 2014, 22:27
hi i did the same thing as karishma and when i got 2551, i thought that cannot be correct as the answer mentions above 40, so my solution must be wrong .. anyway i clicked e and it turned out right. Bunnel & Karishma: how can u guys solve all qs so easily?
_________________
Hope to clear it this time!! GMAT 1: 540 Preparing again



Math Expert
Joined: 02 Sep 2009
Posts: 44423

Re: For every positive even integer n, the function h(n) is defined to be [#permalink]
Show Tags
22 Jun 2014, 09:39



Senior Manager
Status: Stay focused...
Joined: 20 Apr 2014
Posts: 440
Location: United States (MI)
Concentration: Finance, Strategy
Schools: Ross School of Business  Class of 2017
GPA: 3.2
WE: Project Management (Other)

Re: For every positive even integer n, the function h(n) is defined to be [#permalink]
Show Tags
29 Jun 2014, 22:10
imadkho wrote: Thanks Bunuel. It was very helpful. This was my 3rd question on the practice test, I spent a minute without even knowing where to start from, so I made a random guess and moved on. I got 13 incorrect questions out of the 37, but I managed to score 48. thanks again Q48 with 13 incorrect! you must have had a great start and screwed up towards the end, I guess... 'coz I scored a Q50 with 7 wrong answers which were evenly spread ..
_________________
Raves, rants and war stories of First Year MBA Students
Received an offer? Congrats! You might want to 'Negotiate the Offer'.
I'm happy to help if you wanna know about Ross & UMich, but please do not come to me with your GMAT issues or questions. And please add a bit of humor to your questions or you'll bore me to death.



Senior Manager
Joined: 28 Apr 2014
Posts: 266

Re: For every positive even integer n, the function h(n) is defined to be [#permalink]
Show Tags
28 Jul 2014, 02:06
hifunda wrote: Thanks for the explanation. I also got this as my 3rd question, couldn't figure it out, ended up guessing and moving on. Surprising that GMATPrep throws you such hard questions early. I have the same observation. Is this the case in actual GMAT as well ? I also scored 48 on my quant inspite of a few incorrect answers. How will the real GMAT be ? The verbal was quite difficult as well in the GMATPrep exam



Senior Manager
Status: Stay focused...
Joined: 20 Apr 2014
Posts: 440
Location: United States (MI)
Concentration: Finance, Strategy
Schools: Ross School of Business  Class of 2017
GPA: 3.2
WE: Project Management (Other)

Re: For every positive even integer n, the function h(n) is defined to be [#permalink]
Show Tags
28 Jul 2014, 02:41
himanshujovi wrote: I have the same observation. Is this the case in actual GMAT as well ? I also scored 48 on my quant inspite of a few incorrect answers. How will the real GMAT be ?
The verbal was quite difficult as well in the GMATPrep exam Hi Himanshu I found quant pretty easy. If you have appeared for CAT and scored well there (I'm talking 95 percentile+), then you'll be at ease here as well. In case you're not comfy with verbal, then I strongly suggest that you take the free sessions from eGMAT. They also have quite a lot free resource on GMATClub. I used their free stuff for my practice & doubt clearance and was able to score V41. To me it doesn't sound like a coincidence. Cheers to you and all the best.
_________________
Raves, rants and war stories of First Year MBA Students
Received an offer? Congrats! You might want to 'Negotiate the Offer'.
I'm happy to help if you wanna know about Ross & UMich, but please do not come to me with your GMAT issues or questions. And please add a bit of humor to your questions or you'll bore me to death.



Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 8003
Location: Pune, India

Re: For every positive even integer n, the function h(n) is defined to be [#permalink]
Show Tags
28 Jul 2014, 21:32
himanshujovi wrote: hifunda wrote: Thanks for the explanation. I also got this as my 3rd question, couldn't figure it out, ended up guessing and moving on. Surprising that GMATPrep throws you such hard questions early. I have the same observation. Is this the case in actual GMAT as well ? I also scored 48 on my quant inspite of a few incorrect answers. How will the real GMAT be ? The verbal was quite difficult as well in the GMATPrep exam I have known people, who expect to score around 650, to get stuck on first or second question  not many but some. So be prepared for anything. Don't worry much about number of incorrect responses. GMAT will be able to judge your ability as long as you don't mislead it by wasting too much time on 1 or 2 questions or making too many careless mistakes.
_________________
Karishma Veritas Prep  GMAT Instructor My Blog
Get started with Veritas Prep GMAT On Demand for $199
Veritas Prep Reviews



Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 8003
Location: Pune, India

Re: For every positive even integer n, the function h(n) is defined to be [#permalink]
Show Tags
29 Sep 2014, 00:00
1
This post received KUDOS
Expert's post
2
This post was BOOKMARKED
enigma123 wrote: For every positive even integer n, the function h(n) is defined to be the product of all the even integers from 2 to n, inclusive. If p is the smallest prime factor of h(100) +1, then p is?
A. Between 2 and 20 B. Between 10 and 20 C. Between 20 and 30 D. Between 30 and 40 E. Greater than 40
Responding to a pm: Quote: The question boil downs to this equation:
2^50*50!
Now, let's assume this number is n. We know this number is even. So n+1 will have no factors common to n except 1.
But how can we say that n+1 will have factors greater than factors of n? In this question we say that since n has prime factors from 2 to 47, n+1 will have prime factors greater than 47. This part of the solution has left me stumbled.
Let me quote an example: for eg. 34 & 35
34 = 17*2 35 = 5*7
Even though 35 does not share any common factors with 34, it has prime factors less than the largest prime factor of 34 i.e. 17.
So how can we be sure and say 2^2*50!+1 will have the least prime factor greater than 47?
As per my understanding, since 2^50*50! has eaten up all the prime factors from 2 to 47, the only possible factors left for 2^50*50!+1 are greater than 47. Otherwise, 2^50*50!+1 it will end up having prime factors common to 2^50*50!, which is not possible.
Can you help me ensure that my understanding is correct?
You are comparing factors of n with factors of (n+1). You actually have to compare factors of n! with factors of n! + 1. Say n = 4. n! = 1*2*3*4 = 24 n! + 1 = 25 Will 25 have any factors common with n!? No, because n! has all factors from 1 to n. n! + 1 has 5 as a factor which is larger than n. Similarly, say n = 5 n! = 1*2*3*4*5 = 120 n! + 1 = 121 Will 121 have any factors from 1 to 5? No. All these numbers are factors of n! so they cannot be factors of n!+1. Does this make sense?
_________________
Karishma Veritas Prep  GMAT Instructor My Blog
Get started with Veritas Prep GMAT On Demand for $199
Veritas Prep Reviews



Intern
Joined: 05 Sep 2014
Posts: 8

Re: For every positive even integer n, the function h(n) is defined to be [#permalink]
Show Tags
20 Oct 2014, 22:21
Shouldn't 1 be the smallest prime factor of h(100) +1?
Cheers



Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 8003
Location: Pune, India

Re: For every positive even integer n, the function h(n) is defined to be [#permalink]
Show Tags
20 Oct 2014, 22:46
annie2014 wrote: Shouldn't 1 be the smallest prime factor of h(100) +1?
Cheers 1 is not a prime number. The smallest prime number is 2.
_________________
Karishma Veritas Prep  GMAT Instructor My Blog
Get started with Veritas Prep GMAT On Demand for $199
Veritas Prep Reviews



EMPOWERgmat Instructor
Status: GMAT Assassin/CoFounder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 11312
Location: United States (CA)
GRE 1: 340 Q170 V170

Re: For every positive even integer n, the function h(n) is defined to be [#permalink]
Show Tags
26 Feb 2015, 13:36
7
This post received KUDOS
Expert's post
1
This post was BOOKMARKED
Hi All, I've been asked to post this solution here, so here's another way to handle this question: For every positive even integer n, the function h(n) is defined to be the product of all the even integers from 2 to n, inclusive. If p is the smallest prime factor of H(100) + 1, then p is: 1. between 2 and 10 2. between 10 and 20 3. between 20 and 30 4. between 30 and 40 5. greater than 40 The main idea behind this prompt is: "The ONLY number that will divide into X and (X+1) is 1." In other words, NONE of the factors of X will be factors of X+1, EXCEPT for the number 1. Here are some examples: X = 2 X+1 = 3 Factors of 2: 1 and 2 Factors of 3: 1 and 3 ONLY the number 1 is a factor of both. X = 9 X+1 = 10 Factors of 9: 1, 3 and 9 Factors of 10: 1, 2, 5 and 10 ONLY the number 1 is a factor of both. Etc. Since the H(100) is (100)(98)(96)....(4)(2)....we can deduce.... 1) This product will have LOTS of different factors 2) NONE of those factors will divide into H(100) + 1. H(100) contains all of the primes from 2 through 47, inclusive (the 47 can be "found" in the "94"), so NONE of those will be in H(100) + 1. We don't even have to calculate which prime factor is smallest in H(100) + 1; we know that it MUST be a prime greater than 47....and there's only one answer that fits. Final Answer: GMAT assassins aren't born, they're made, Rich
_________________
760+: Learn What GMAT Assassins Do to Score at the Highest Levels Contact Rich at: Rich.C@empowergmat.com
Rich Cohen
CoFounder & GMAT Assassin
Special Offer: Save $75 + GMAT Club Tests Free
Official GMAT Exam Packs + 70 Pt. Improvement Guarantee www.empowergmat.com/
***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************



Math Expert
Joined: 02 Sep 2009
Posts: 44423

Re: For every positive even integer n, the function h(n) is defined to be [#permalink]
Show Tags
26 Feb 2015, 13:38
EMPOWERgmatRichC wrote: Hi All, I've been asked to post this solution here, so here's another way to handle this question: For every positive even integer n, the function h(n) is defined to be the product of all the even integers from 2 to n, inclusive. If p is the smallest prime factor of H(100) + 1, then p is: 1. between 2 and 10 2. between 10 and 20 3. between 20 and 30 4. between 30 and 40 5. greater than 40 The main idea behind this prompt is: "The ONLY number that will divide into X and (X+1) is 1." In other words, NONE of the factors of X will be factors of X+1, EXCEPT for the number 1. Here are some examples: X = 2 X+1 = 3 Factors of 2: 1 and 2 Factors of 3: 1 and 3 ONLY the number 1 is a factor of both. X = 9 X+1 = 10 Factors of 9: 1, 3 and 9 Factors of 10: 1, 2, 5 and 10 ONLY the number 1 is a factor of both. Etc. Since the H(100) is (100)(98)(96)....(4)(2)....we can deduce.... 1) This product will have LOTS of different factors 2) NONE of those factors will divide into H(100) + 1. H(100) contains all of the primes from 2 through 47, inclusive (the 47 can be "found" in the "94"), so NONE of those will be in H(100) + 1. We don't even have to calculate which prime factor is smallest in H(100) + 1; we know that it MUST be a prime greater than 47....and there's only one answer that fits. Final Answer: GMAT assassins aren't born, they're made, Rich __________ Thank you, Rich!
_________________
New to the Math Forum? Please read this: Ultimate GMAT Quantitative Megathread  All You Need for Quant  PLEASE READ AND FOLLOW: 12 Rules for Posting!!! Resources: GMAT Math Book  Triangles  Polygons  Coordinate Geometry  Factorials  Circles  Number Theory  Remainders; 8. Overlapping Sets  PDF of Math Book; 10. Remainders  GMAT Prep Software Analysis  SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS)  Tricky questions from previous years.
Collection of Questions: PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.
What are GMAT Club Tests? Extrahard Quant Tests with Brilliant Analytics



SVP
Joined: 08 Jul 2010
Posts: 2017
Location: India
GMAT: INSIGHT
WE: Education (Education)

Re: For every positive even integer n, the function h(n) is defined to be [#permalink]
Show Tags
12 Nov 2015, 09:06
enigma123 wrote: For every positive even integer n, the function h(n) is defined to be the product of all the even integers from 2 to n, inclusive. If p is the smallest prime factor of h(100) +1, then p is?
A. Between 2 and 20 B. Between 10 and 20 C. Between 20 and 30 D. Between 30 and 40 E. Greater than 40
As per the definition of the question h(100) = 2 x 4 x 6 x 8 x 10 x 12 x 14 ... and so on...98 x 100 (Total 50 terms) => h(100) = 2^50 (1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 x 10......and so on...x 48 x 49 x 50) This means h(100) is multiple of all prime numbers between 1 and 50 therefore h(100)+1 will leave a remainder of 1 when divided by any prime number from 1 to 50 therefore, p, which is a factor of h(100)+1, will certainly be greater than a prime numbers greater than 50 Hence, "p" must be greater than 40 as per the following options Answer: Option E
_________________
Prosper!!! GMATinsight Bhoopendra Singh and Dr.Sushma Jha email: info@GMATinsight.com I Call us : +919999687183 / 9891333772 Online OneonOne Skype based classes and Classroom Coaching in South and West Delhi http://www.GMATinsight.com/testimonials.html
22 ONLINE FREE (FULL LENGTH) GMAT CAT (PRACTICE TESTS) LINK COLLECTION



Intern
Joined: 13 Nov 2015
Posts: 14

Re: For every positive even integer n, the function h(n) is defined to be [#permalink]
Show Tags
16 Dec 2015, 17:58
Thanks! Really helpful.



Director
Joined: 10 Mar 2013
Posts: 578
Location: Germany
Concentration: Finance, Entrepreneurship
GPA: 3.88
WE: Information Technology (Consulting)

Re: For every positive even integer n, the function h(n) is defined to be [#permalink]
Show Tags
23 Dec 2015, 16:13
EMPOWERgmatRichC wrote: Hi All, I've been asked to post this solution here, so here's another way to handle this question: For every positive even integer n, the function h(n) is defined to be the product of all the even integers from 2 to n, inclusive. If p is the smallest prime factor of H(100) + 1, then p is: 1. between 2 and 10 2. between 10 and 20 3. between 20 and 30 4. between 30 and 40 5. greater than 40 The main idea behind this prompt is: "The ONLY number that will divide into X and (X+1) is 1." In other words, NONE of the factors of X will be factors of X+1, EXCEPT for the number 1. Here are some examples: X = 2 X+1 = 3 Factors of 2: 1 and 2 Factors of 3: 1 and 3 ONLY the number 1 is a factor of both. X = 9 X+1 = 10 Factors of 9: 1, 3 and 9 Factors of 10: 1, 2, 5 and 10 ONLY the number 1 is a factor of both. Etc. Since the H(100) is (100)(98)(96)....(4)(2)....we can deduce.... 1) This product will have LOTS of different factors 2) NONE of those factors will divide into H(100) + 1. H(100) contains all of the primes from 2 through 47, inclusive (the 47 can be "found" in the "94"), so NONE of those will be in H(100) + 1. We don't even have to calculate which prime factor is smallest in H(100) + 1; we know that it MUST be a prime greater than 47....and there's only one answer that fits. Final Answer: GMAT assassins aren't born, they're made, Rich fastest approach till now. +1 from me.
_________________
When you’re up, your friends know who you are. When you’re down, you know who your friends are.
Share some Kudos, if my posts help you. Thank you !
800Score ONLY QUANT CAT1 51, CAT2 50, CAT3 50 GMAT PREP 670 MGMAT CAT 630 KAPLAN CAT 660



Math Expert
Joined: 02 Aug 2009
Posts: 5731

Re: For every positive even integer n, the function h(n) is defined to be [#permalink]
Show Tags
31 Jan 2016, 01:07
gnikhilreddy143 wrote: For every positive even integer n, the function h(n) is defined to be the product of all even integers from 2 to n, inclusive. If p is the smallest prime factor of h(100)+1, then p is
a) between 2 and 10 b) between 10 and 20 c) between 20 and 30 d) between 30 and 40 e) greater than 40 Hi, without any calculations we can make out that h(n) will consist of products of all numbers till 50and 2^50, as it is even integers so 100/2.. therefore when we add 1 to this product , it will not be a multiple of any number till 50.. so the smallest prime factor has to be >50.. E.. lets solve it.. h(100)= 2*4*6...*100.. = 2*1*2*2*2*3...2*50= 2^50*1*2*...50.. h(100)+1= 2^50*1*2*...50 +1.. so prime factor>50.. ans E >40 NOTE: Merging topic. Please type the first few letters as TOPIC name correctly
_________________
Absolute modulus :http://gmatclub.com/forum/absolutemodulusabetterunderstanding210849.html#p1622372 Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
GMAT online Tutor



SVP
Joined: 12 Sep 2015
Posts: 2161
Location: Canada

Re: For every positive even integer n, the function h(n) is defined to be [#permalink]
Show Tags
31 Jan 2016, 01:30
Quote: For every positive even integer n, the function h(n) is defined to be the product of all even integers from 2 to n, inclusive. If p is the smallest prime factor of h(100) + 1, the p is
A: Between 2 & 10 B: Between 10 & 20 C: Between 20 & 30 D: Between 30 & 40 E: Greater than 40 Important Concept: If integer k is greater than 1, and k is a factor (divisor) of N, then k is not a divisor of N+1For example, since 7 is a factor of 350, we know that 7 is not a factor of (350 +1) Similarly, since 8 is a factor of 312, we know that 8 is not a factor of 313 Now let’s examine h(100) h(100) = (2)(4)(6)(8)….(96)(98)(100) = (2x 1)(2x 2)(2x 3)(2x 4)....(2x 48)(2x 49)(2x 50) Factor out all of the 2's to get: h(100) = [2^50][ (1)(2)(3)(4)….(48)(49)(50)] Since 2 is in the product of h(100), we know that 2 is a factor of h(100), which means that 2 is not a factor of h(100) +1 (based on the above rule) Similarly, since 3 is in the product of h(100), we know that 3 is a factor of h(100), which means that 3 is not a factor of h(100) +1 (based on the above rule) Similarly, since 5 is in the product of h(100), we know that 5 is a factor of h(100), which means that 5 is not a factor of h(100) +1 (based on the above rule) . . . . Similarly, since 47 is in the product of h(100), we know that 47 is a factor of h(100), which means that 47 is not a factor of h(100) +1 (based on the above rule) So, we can see that none of the primes from 2 to 47 can be factors of h(100)+1, which means the smallest prime factor of h(100)+1 must be greater than 47. Answer = E Cheers, Brent
_________________
Brent Hanneson – Founder of gmatprepnow.com



Intern
Joined: 17 Dec 2015
Posts: 7
Concentration: Marketing, International Business
WE: Information Technology (Consulting)

Re: For every positive even integer n, the function h(n) is defined to be [#permalink]
Show Tags
31 Jan 2016, 05:56
neo656 wrote: imadkho wrote: Thanks Bunuel. It was very helpful. This was my 3rd question on the practice test, I spent a minute without even knowing where to start from, so I made a random guess and moved on. I got 13 incorrect questions out of the 37, but I managed to score 48. thanks again Q48 with 13 incorrect! you must have had a great start and screwed up towards the end, I guess... 'coz I scored a Q50 with 7 wrong answers which were evenly spread .. I have got 49 with 13 incorrect in GMAT Prep Practice Test1. However, my verbal score was screwed up, and it was 23. I have just started my preparation.
_________________
Thanks & Regards Nikhil



Intern
Joined: 24 Feb 2015
Posts: 5

Re: For every positive even integer n, the function h(n) is defined to be [#permalink]
Show Tags
09 Jul 2016, 18:44
Bunuel, thanks for the help you are giving to all of us! Really clear explanation!



Manager
Joined: 03 Aug 2016
Posts: 113
Location: India
Concentration: Operations, Entrepreneurship
GPA: 4
WE: Design (Transportation)

Re: For every positive even integer n, the function h(n) is defined to be [#permalink]
Show Tags
09 Nov 2016, 02:28
Hello I didn't understand how the formula works Product of terms = Average * number of terms as per the formula h(100) = 2550 But if I multiply 2 *100 = 200 *4 = 800 * 6 = 4800 > 2550 ( I have multiplied only 4 numbers, I have to multiply 8,10...,98. SO the h(100) will be much greater ? Am I missing anything? Alok VeritasPrepKarishma wrote: enigma123 wrote: For every positive even integer n, the function h(n) is defined to be the product of all the even integers from 2 to n, inclusive. If p is the smallest prime factor of h(100) +1, then p is?
A. between 2 and 20 B. between 10 and 20 C. between 20 and 30 D. between 30 and 40 E. greater than 40
This is how I am trying to solve this. Please help me if you think I am not right. OA is not provided in the book.
h(100) = 2 * 4 * 6 ****************100
Tn = a1 + (n1) d(1) where Tn is the last term, a1 is the first term and d is the common difference of the evenly spaced set.
100 = 2 + (n1) 2 n = 50
Product of terms = Average * number of terms
Average = (a1+an)/2 Therefore average = 102/2 = 51 Product of the series = 51*50 = 2550.
H(100) + 1 = 2550+1 = 2551 which is prime. And prime numbers have exactly 2 factors 1 and the number itself. Therefore for me D is the answer i.e. < 10 Check out this post for detailed theory involved in this question: http://www.veritasprep.com/blog/2011/09 ... hpartii/



Manager
Joined: 03 Oct 2013
Posts: 84

Re: For every positive even integer n, the function h(n) is defined to be [#permalink]
Show Tags
17 Nov 2016, 10:12
h(100)+1 = (2*4*6*8....100)+1 = ((2*1)*(2*2)*(2*3)*(2*4)*.....(2*50))+1 = (2^50)*(1*2*3*4*...*50)+1 the first part has all numbers (including prime) as it's factors. First part+1 is a consecutive number so they do not share any common factors (other than 1, which neither prime nor composite). Therefore the smallest prime factor for h(100)+1 is greater than 50. Answer : E
_________________
P.S. Don't forget to give Kudos on the left if you like the solution




Re: For every positive even integer n, the function h(n) is defined to be
[#permalink]
17 Nov 2016, 10:12



Go to page
Previous
1 2 3
Next
[ 53 posts ]



