Author 
Message 
TAGS:

Hide Tags

Manager
Joined: 16 Feb 2012
Posts: 205
Concentration: Finance, Economics

a, b, c, and d are positive consecutive integers and a < b < [#permalink]
Show Tags
17 Aug 2013, 10:34
1
This post received KUDOS
8
This post was BOOKMARKED
Question Stats:
81% (01:11) correct 19% (01:15) wrong based on 255 sessions
HideShow timer Statistics
a, b, c, and d are positive consecutive integers and a < b < c < d. If the product of b, c, and d is twice that of a, b, and c, then bc = A 2 B 6 C 12 D 20 E 30
Official Answer and Stats are available only to registered users. Register/ Login.
_________________
Kudos if you like the post!
Failing to plan is planning to fail.



Director
Joined: 14 Dec 2012
Posts: 812
Location: India
Concentration: General Management, Operations
GPA: 3.6

Re: a, b, c, and d are positive consecutive integers and a < b < [#permalink]
Show Tags
17 Aug 2013, 10:44
3
This post received KUDOS
2
This post was BOOKMARKED
Stiv wrote: a, b, c, and d are positive consecutive integers and a < b < c < d. If the product of b, c, and d is twice that of a, b, and c, then bc = A 2 B 6 C 12 D 20 E 30 a, b, c, and d are positive consecutive integers since a b c d are consecutive integers
therefore \(d= a+3\) now given \(2abc = bcd\) \(bc(2ad) = 0\) since they are positive hence bc cant be equal to 0therefore \(2ad = 0\) putting \(d = a+3\) \(2aa3=0.\) \(a=3\) therefore \(b= 4 and c= 5\) hence bc = \(4*5 = 20\) HENCE D
_________________
When you want to succeed as bad as you want to breathe ...then you will be successfull....
GIVE VALUE TO OFFICIAL QUESTIONS...
GMAT RCs VOCABULARY LIST: http://gmatclub.com/forum/vocabularylistforgmatreadingcomprehension155228.html learn AWA writing techniques while watching video : http://www.gmatprepnow.com/module/gmatanalyticalwritingassessment : http://www.youtube.com/watch?v=APt9ITygGss



Senior Manager
Joined: 10 Jul 2013
Posts: 318

Re: a, b, c, and d are positive consecutive integers and a < b < [#permalink]
Show Tags
17 Aug 2013, 10:51
Stiv wrote: a, b, c, and d are positive consecutive integers and a < b < c < d. If the product of b, c, and d is twice that of a, b, and c, then bc = A 2 B 6 C 12 D 20 E 30 Here, bcd = 2 abc , so, d = 2a and we know, a<b<c<d so the series is like, 3<4<5<6 Finally, bc = 4 × 5 = 20
_________________
Asif vai.....



Study Buddy Forum Moderator
Joined: 04 Sep 2016
Posts: 877
Location: India
WE: Engineering (Other)

Re: a, b, c, and d are positive consecutive integers and a < b < [#permalink]
Show Tags
10 Apr 2018, 11:44
Bunuel niks18 chetan2uQuote: a, b, c, and d are positive consecutive integers and a < b < c < d. If the product of b, c, and d is twice that of a, b, and c, then bc = A 2 B 6 C 12 D 20 E 30 My sol matched with blueseas let me know if there is any better approach?
_________________
It's the journey that brings us happiness not the destination.



Manager
Joined: 08 Sep 2016
Posts: 56

Re: a, b, c, and d are positive consecutive integers and a < b < [#permalink]
Show Tags
10 Apr 2018, 14:40
Asifpirlo wrote: Stiv wrote: a, b, c, and d are positive consecutive integers and a < b < c < d. If the product of b, c, and d is twice that of a, b, and c, then bc = A 2 B 6 C 12 D 20 E 30 Here, bcd = 2 abc , so, d = 2a and we know, a<b<c<d so the series is like, 3<4<5<6 Finally, bc = 4 × 5 = 20 I did the problem this way and got the correct answer, but I think the primary reason why this approach worked is because we are told that the variables were positive integers. I don't think this approach would have worked if the sign wasn't mentioned.



PS Forum Moderator
Joined: 25 Feb 2013
Posts: 1045
Location: India
GPA: 3.82

a, b, c, and d are positive consecutive integers and a < b < [#permalink]
Show Tags
10 Apr 2018, 18:54
adkikani wrote: Bunuel niks18 chetan2uQuote: a, b, c, and d are positive consecutive integers and a < b < c < d. If the product of b, c, and d is twice that of a, b, and c, then bc = A 2 B 6 C 12 D 20 E 30 My sol matched with blueseas let me know if there is any better approach? Hi adkikani, I am not sure about "Better" but yes there are other approaches to solve the problem. Now it is also given that \(2abc=bcd =>d=2a\). You can work backwards through options  2=1*2, hence b=1,c=2,d=3 and a=0, which is not possible as a is positive. 6=2*3, hence b=2,c=3,d=4 and a=1, but d=2a, Hence ignore 12=3*4, hence b=3,c=4,d=5 and a=2, again not possible 20=4*5, hence b=4, c=5, d=6 and a=3. here d=2a. Hence our answer 30=5*6, hence b=5,c=6,d=7 and a=4, which is not possible



Study Buddy Forum Moderator
Joined: 04 Sep 2016
Posts: 877
Location: India
WE: Engineering (Other)

Re: a, b, c, and d are positive consecutive integers and a < b < [#permalink]
Show Tags
10 Apr 2018, 19:26
1
This post received KUDOS
niks18Quote: By looking at the answer choices, you should realize that both\(b\) & \(d\) has to be Even. Can you verify highlighted text again? Fundamentally, EITHER of two numbers is suff for product to be EVEN. Is your rationale based on the fact that a,b,c,d are consecutive integers?
_________________
It's the journey that brings us happiness not the destination.



PS Forum Moderator
Joined: 25 Feb 2013
Posts: 1045
Location: India
GPA: 3.82

a, b, c, and d are positive consecutive integers and a < b < [#permalink]
Show Tags
10 Apr 2018, 19:50
adkikani wrote: niks18Quote: By looking at the answer choices, you should realize that both\(b\) & \(d\) has to be Even. Can you verify highlighted text again? Fundamentally, EITHER of two numbers is suff for product to be EVEN. Is your rationale based on the fact that a,b,c,d are consecutive integers? Hi adkikaniMy bad, I read the question as b*d instead of b*c. Yes you are correct, in your observation. I have edited my solution




a, b, c, and d are positive consecutive integers and a < b <
[#permalink]
10 Apr 2018, 19:50






