Author 
Message 
TAGS:

Hide Tags

Manager
Joined: 28 Aug 2010
Posts: 241

A total of 30 percent of the geese included in a certain [#permalink]
Show Tags
Updated on: 07 Oct 2013, 01:29
47
This post was BOOKMARKED
Question Stats:
67% (01:08) correct 33% (01:06) wrong based on 824 sessions
HideShow timer Statistics
A total of 30 percent of the geese included in a certain migration study were male. If some of the geese migrated during the study and 20 percent of the migrating geese were male, what was the ratio of the migration rate for the male geese to the migration rate for the female geese? [Migration rate for geese of a certain sex = (number of geese of that sex migrating) / (total number of geese of that sex)] A. 1/4 B. 7/12 C. 2/3 D. 7/8 E. 8/7
Official Answer and Stats are available only to registered users. Register/ Login.
_________________
Verbal:newtotheverbalforumpleasereadthisfirst77546.html Math: newtothemathforumpleasereadthisfirst77764.html Gmat: everythingyouneedtoprepareforthegmatrevised77983.html  Ajit
Originally posted by ajit257 on 05 Jan 2011, 18:45.
Last edited by Bunuel on 07 Oct 2013, 01:29, edited 1 time in total.
Edited the OA.



Manager
Joined: 13 Aug 2010
Posts: 197

Re: A total of 30 percent of the geese [#permalink]
Show Tags
05 Jan 2011, 23:05
Let there be 100 geese. Out of these since there were 30% male then there were 70 females, let the number of migrating birds be X, out of the ones migrating 20% were males so .8x where females. so, 7/8 (D)



Retired Moderator
Joined: 02 Sep 2010
Posts: 775
Location: London

Re: A total of 30 percent of the geese [#permalink]
Show Tags
06 Jan 2011, 00:24
20
This post received KUDOS
19
This post was BOOKMARKED
ajit257 wrote: A total of 30 percent of the geese included in a certain migration study were male. If some of the geese migrated during the study and 20 percent of the migrating geese were male, what was the ratio of the migration rate for the male geese to the migration rate for the female geese? [Migration rate for geese of a certain sex = (number of geese of that sex migrating) / (total number of geese of that sex)]
A. 1/4 B. 7/12 C. 2/3 D. 7/8 E. 8/7 Let there be g geese, of which 0.3g are male and 0.7g are female Lets say m geese migrated, 0.2m are male and 0.8m are female Migration Rate Male = 0.2m / 0.3g = (2/3)*(m/g) Migration Rate Female = 0.8m / 0.7g = (8/7)*(m/g) Ratio of migration rates = (2/3) / (8/7) = 7/12 Answer is (b)
_________________
Math writeups 1) Algebra101 2) Sequences 3) Set combinatorics 4) 3D geometry
My GMAT story
GMAT Club Premium Membership  big benefits and savings



Manager
Joined: 03 Nov 2009
Posts: 65

Re: A total of 30 percent of the geese [#permalink]
Show Tags
06 Jan 2011, 00:49
3
This post received KUDOS
3
This post was BOOKMARKED
Let' take the Number of geese to be 100.
Male = 30. Female = 70.
Now the second part of the Q, Let's take the Number migrated to be 20.
So we have 20 geese that migrated and out of that 20% are male i.e 20/100 *20 = 4 Geese (Males)
And now we know out of the total 20 geese , 4 are male , then 16 have to be female.
Now the ratio part , Male Geese Ratios = 4/30 = 2/15.  A
Female Geese Ratios =16/70=8/35  B
Cross Multiply Equations A and B and you get =7/12 .
Ans B



Manager
Joined: 30 May 2013
Posts: 172
Location: India
Concentration: Entrepreneurship, General Management
GPA: 3.82

Re: A total of 30 percent of the geese [#permalink]
Show Tags
07 Oct 2013, 05:54
DaVagabond wrote: Let' take the Number of geese to be 100.
Male = 30. Female = 70.
Now the second part of the Q, Let's take the Number migrated to be 20.
So we have 20 geese that migrated and out of that 20% are male i.e 20/100 *20 = 4 Geese (Males)
And now we know out of the total 20 geese , 4 are male , then 16 have to be female.
Now the ratio part , Male Geese Ratios = 4/30 = 2/15.  A
Female Geese Ratios =16/70=8/35  B
Cross Multiply Equations A and B and you get =7/12 .
Ans B Hi all, i too tried the same method and its taking more than 3 Mins. Please tell if there is any fast solution method. Regards, Rrsnathan



Manager
Joined: 29 Aug 2013
Posts: 75
Location: United States
Concentration: Finance, International Business
GMAT 1: 590 Q41 V29 GMAT 2: 540 Q44 V20
GPA: 3.5
WE: Programming (Computer Software)

Re: A total of 30 percent of the geese [#permalink]
Show Tags
08 Oct 2013, 08:53
11
This post received KUDOS
2
This post was BOOKMARKED
rrsnathan wrote: DaVagabond wrote: Let' take the Number of geese to be 100.
Male = 30. Female = 70.
Now the second part of the Q, Let's take the Number migrated to be 20.
So we have 20 geese that migrated and out of that 20% are male i.e 20/100 *20 = 4 Geese (Males)
And now we know out of the total 20 geese , 4 are male , then 16 have to be female.
Now the ratio part , Male Geese Ratios = 4/30 = 2/15.  A
Female Geese Ratios =16/70=8/35  B
Cross Multiply Equations A and B and you get =7/12 .
Ans B Hi all, i too tried the same method and its taking more than 3 Mins. Please tell if there is any fast solution method. Regards, Rrsnathan say 100 are geese.. 30% means 30 are male and 70 are female. Now x geese migrates, Therefore \(\frac{x}{5}\) are male (since 20% of migrating geeses are male) and hence \(\frac{4x}{5}\) are female Therefore \(\frac{Migration rate male}{Migration rate female}\) = {(x/5)/30} / {(4x/5)/70} Solving we get, 7/12 as answer. Consider Kudos if the post helped.



Intern
Joined: 23 May 2016
Posts: 10

Re: A total of 30 percent of the geese included in a certain [#permalink]
Show Tags
01 Jun 2016, 17:57
If we use the formula they give us
Isnt the migration rate the following:
Males = # geese migrating / total # of geese in sex = 0.2 (0.3x) / 0.3 Females = 0.8 * 0.7 / 0.7
Can someone help please explain why it is not the above?



Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 8025
Location: Pune, India

Re: A total of 30 percent of the geese included in a certain [#permalink]
Show Tags
01 Jun 2016, 23:13
rjivani wrote: If we use the formula they give us
Isnt the migration rate the following:
Males = # geese migrating / total # of geese in sex = 0.2 (0.3x) / 0.3 Females = 0.8 * 0.7 / 0.7
Can someone help please explain why it is not the above? 0.2 * (0.3x) is a problem. The questions says that 20% of the geese migrating were males. It doesn't say that 20% of males migrated. Sp if there were 100 geese in all, 30 were males. The question does NOT say that 20% of these 30 migrated. Say, if half the total geese migrated, 50 migrated. Out of these 50, 20% were male i.e. 10 were male. SO we need to take 20% of migrated geese, not the 20% of male population. Does this sort out your problem?
_________________
Karishma Veritas Prep  GMAT Instructor My Blog
Get started with Veritas Prep GMAT On Demand for $199
Veritas Prep Reviews



Manager
Joined: 13 Dec 2013
Posts: 163
Location: United States (NY)
Concentration: Nonprofit, International Business
GMAT 1: 710 Q46 V41 GMAT 2: 720 Q48 V40
GPA: 4
WE: Consulting (Consulting)

Re: A total of 30 percent of the geese included in a certain [#permalink]
Show Tags
23 Mar 2017, 19:45
1
This post received KUDOS
Taking 100 as the number of geese in the study, 30 are male and 70 are female. Setting the number of geese that migrate as 5x, the number of male geese migrating is x (20%), and the number of female geese migrating is 4x (80%).
Ratio = (x/30)/(4x/70) = 70x/120x = 7/12
Kudos if you agree!
Please reply if you have a better solution.



Target Test Prep Representative
Status: Head GMAT Instructor
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 2298

Re: A total of 30 percent of the geese included in a certain [#permalink]
Show Tags
27 Mar 2017, 17:28
ajit257 wrote: A total of 30 percent of the geese included in a certain migration study were male. If some of the geese migrated during the study and 20 percent of the migrating geese were male, what was the ratio of the migration rate for the male geese to the migration rate for the female geese? [Migration rate for geese of a certain sex = (number of geese of that sex migrating) / (total number of geese of that sex)]
A. 1/4 B. 7/12 C. 2/3 D. 7/8 E. 8/7 We can let t = the total number of geese before migration; thus, the number of male geese = 0.3t and the number of female geese = 0.7t. If we let the number of migrating geese = m, then the number of male migrating geese = 0.2m and the number of female migrating geese = 0.8m. Thus, the migration rate for the male geese is 0.2m/0.3t = 2m/3t and the migration rate for the female geese is 0.8m/0.7t = 8m/7t. Thus, the ratio of male migration rate to female migration rate is: (2m/3t)/(8m/7t) = (7t x 2m)/(3t x 8m) = (14mt)/(24mt) = 14/24 = 7/12. Answer: B
_________________
Jeffery Miller
Head of GMAT Instruction
GMAT Quant SelfStudy Course
500+ lessons 3000+ practice problems 800+ HD solutions



Manager
Joined: 24 Nov 2014
Posts: 197

Re: A total of 30 percent of the geese included in a certain [#permalink]
Show Tags
06 Jan 2018, 18:35
rrsnathan wrote: DaVagabond wrote: Let' take the Number of geese to be 100.
Male = 30. Female = 70.
Now the second part of the Q, Let's take the Number migrated to be 20.
So we have 20 geese that migrated and out of that 20% are male i.e 20/100 *20 = 4 Geese (Males)
And now we know out of the total 20 geese , 4 are male , then 16 have to be female.
Now the ratio part , Male Geese Ratios = 4/30 = 2/15.  A
Female Geese Ratios =16/70=8/35  B
Cross Multiply Equations A and B and you get =7/12 .
Ans B Hi all, i too tried the same method and its taking more than 3 Mins. Please tell if there is any fast solution method. Regards, Rrsnathan You could use the same method, but with simpler numbers. 30 males 70 females Any 20/80 ratio for males migrating to females migrating will work. So, you could use the following. 10 males migrated 40 females migrated male migration ratio: 10/30 = 1/3 female migration ratio: 40/70 = 4/7 (1/3)/(4/7) = 7/12 Choose B, and you are on to the next question. Enjoy the GAME!
_________________
Marty Murray GMAT Coach m.w.murray@hotmail.com http://infinitemindprep.com



Intern
Joined: 20 Nov 2017
Posts: 16

Re: A total of 30 percent of the geese included in a certain [#permalink]
Show Tags
06 Jan 2018, 23:05
What level question is this? Sent from my SMN910C using GMAT Club Forum mobile app



Math Expert
Joined: 02 Sep 2009
Posts: 44656

Re: A total of 30 percent of the geese included in a certain [#permalink]
Show Tags
07 Jan 2018, 00:40



Intern
Joined: 30 Jun 2017
Posts: 11

Re: A total of 30 percent of the geese included in a certain [#permalink]
Show Tags
08 Feb 2018, 17:27
MartyMurray wrote: rrsnathan wrote: DaVagabond wrote: Let' take the Number of geese to be 100.
Male = 30. Female = 70.
Now the second part of the Q, Let's take the Number migrated to be 20.
So we have 20 geese that migrated and out of that 20% are male i.e 20/100 *20 = 4 Geese (Males)
And now we know out of the total 20 geese , 4 are male , then 16 have to be female.
Now the ratio part , Male Geese Ratios = 4/30 = 2/15.  A
Female Geese Ratios =16/70=8/35  B
Cross Multiply Equations A and B and you get =7/12 .
Ans B Hi all, i too tried the same method and its taking more than 3 Mins. Please tell if there is any fast solution method. Regards, Rrsnathan You could use the same method, but with simpler numbers. 30 males 70 females Any 20/80 ratio for males migrating to females migrating will work. So, you could use the following. 10 males migrated 40 females migrated male migration ratio: 10/30 = 1/3 female migration ratio: 40/70 = 4/7 (1/3)/(4/7) = 7/12 Choose B, and you are on to the next question. Enjoy the GAME! Great explanation! Can someone quickly point out why you divide (1/3) by (4/7) in order to take the ratio of those? Thanks



Math Expert
Joined: 02 Aug 2009
Posts: 5777

Re: A total of 30 percent of the geese included in a certain [#permalink]
Show Tags
08 Feb 2018, 20:08
hjli89 wrote: MartyMurray wrote: Let' take the Number of geese to be 100. You could use the same method, but with simpler numbers. 30 males 70 females Any 20/80 ratio for males migrating to females migrating will work. So, you could use the following. 10 males migrated 40 females migrated male migration ratio: 10/30 = 1/3 female migration ratio: 40/70 = 4/7 (1/3)/(4/7) = 7/12 Choose B, and you are on to the next question. Enjoy the GAME! Great explanation! Can someone quickly point out why you divide (1/3) by (4/7) in order to take the ratio of those? Thanks [/quote] [Migration rate for geese of a certain sex = (number of geese of that sex migrating) / (total number of geese of that sex)] the migration rate for the male geese = 1/3 the migration rate for the female geese=4/7 BUT we have to find RATIO of these rates: "theratio of the migration rate for the male geese to the migration rate for the female geese?" That is why we divide 1/3 by 4/7 Hope it helps
_________________
Absolute modulus :http://gmatclub.com/forum/absolutemodulusabetterunderstanding210849.html#p1622372 Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
GMAT online Tutor




Re: A total of 30 percent of the geese included in a certain
[#permalink]
08 Feb 2018, 20:08






