Author 
Message 
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 44651

A certain zoo has mammal and reptiles and birds, and no other animals. [#permalink]
Show Tags
27 Sep 2015, 12:19
1
This post received KUDOS
Expert's post
2
This post was BOOKMARKED
Question Stats:
76% (01:11) correct 24% (00:57) wrong based on 126 sessions
HideShow timer Statistics



SVP
Joined: 12 Sep 2015
Posts: 2308
Location: Canada

Re: A certain zoo has mammal and reptiles and birds, and no other animals. [#permalink]
Show Tags
27 Sep 2015, 13:04
Bunuel wrote: A certain zoo has mammal and reptiles and birds, and no other animals. The ratio of mammals to reptiles to birds is 11: 8:5. How many birds are in the zoo?
(1) there are twelve more mammals in the zoo than there are reptiles
(2) if the zoo acquired 16 more mammals, the ratio of mammals to birds would be 3:1
Kudos for a correct solution. Target question: How many birds are in the zoo? Given: The ratio of mammals to reptiles to birds is 11: 8:5. Given this ratio, we could say that there are: 11x mammals 8x reptiles 5x birds for some value of x. Statement 1: there are twelve more mammals in the zoo than there are reptiles We can write: number of mammals = number of reptiles + 12 Or we can write: 11x = 8x + 12 Solve to get x = 4 Once we know the value of x, we can see that the number of birds = 5x = (5)(4) = 20Since we can answer the target question with certainty, statement 1 is SUFFICIENT Statement 2: if the zoo acquired 16 more mammals, the ratio of mammals to birds would be 3:1 So, (current number of mammals + 16)/(current number birds) = 3/1 Or we can write: (11x +16)/5x = 3/1 Cross multiply to get: 11x + 16 = 15x Solve, to get x = 4 Once we know the value of x, we can see that the number of birds = 5x = (5)(4) = 20Since we can answer the target question with certainty, statement 2 is SUFFICIENT Answer = D Cheers, Brent
_________________
Brent Hanneson – Founder of gmatprepnow.com



Manager
Joined: 29 Jul 2015
Posts: 159

Re: A certain zoo has mammal and reptiles and birds, and no other animals. [#permalink]
Show Tags
27 Sep 2015, 14:07
Bunuel wrote: A certain zoo has mammal and reptiles and birds, and no other animals. The ratio of mammals to reptiles to birds is 11: 8:5. How many birds are in the zoo?
(1) there are twelve more mammals in the zoo than there are reptiles
(2) if the zoo acquired 16 more mammals, the ratio of mammals to birds would be 3:1
Kudos for a correct solution. Statement 1: Let x be the number of mammals and y be the number of reptiles. Then, x/y=11/8 or 8x=11y There are 12 more mammals in the zoo than reptiles. or x=12+y putting this in above equation we have 8(12+y)=11y or 96+8y=11y or 96=3y or y=32 So there are total 32 reptiles. There are 8 reptiles in the ratio.So the common multiplier is 32/8=4 and the number of birds is 5*4=20. SUFFICIENT Statement 2: Let x be the common multiplier. When zoo acquired 16 more mammals, the ratio of mammals to birds would be 3:1 or \(\frac{11x+16}{5x}=\frac{3}{1}\) or 11x+16=15x or 4x=16 or x=4 So the number of birds will be 4*5=20 SUFFICIENT Answer: D



Intern
Joined: 13 Nov 2014
Posts: 48
GMAT 1: 590 Q42 V29 GMAT 2: 630 Q47 V29

Re: A certain zoo has mammal and reptiles and birds, and no other animals. [#permalink]
Show Tags
27 Sep 2015, 19:44
Bunuel wrote: A certain zoo has mammal and reptiles and birds, and no other animals. The ratio of mammals to reptiles to birds is 11: 8:5. How many birds are in the zoo?
(1) there are twelve more mammals in the zoo than there are reptiles
(2) if the zoo acquired 16 more mammals, the ratio of mammals to birds would be 3:1
Kudos for a correct solution. by 1st statement diff between ratio is 3 units, and those 3 units are equal to 12, hence 1 unit equal to 4, so birds are 20,sufficient. by 2nd statement, 16 more additions in mammals will make that ratio 15:8:5, hence 4 units of ratio are equal to 16, again by above method the ans is same hence ans is D
_________________
 Consider Cudos if you like this post. 



Director
Status: It's near  I can see.
Joined: 13 Apr 2013
Posts: 736
Location: India
Concentration: International Business, Operations
GPA: 3.01
WE: Engineering (Consulting)

A certain zoo has mammal and reptiles and birds, and no other animals. [#permalink]
Show Tags
28 Sep 2015, 00:26
Bunuel wrote: A certain zoo has mammal and reptiles and birds, and no other animals. The ratio of mammals to reptiles to birds is 11: 8:5. How many birds are in the zoo?
(1) there are twelve more mammals in the zoo than there are reptiles
(2) if the zoo acquired 16 more mammals, the ratio of mammals to birds would be 3:1
Kudos for a correct solution. My Solution: Initial ratio of mammal to reptiles to birds 11:8:5. Lets say Mammals=11x, Reptiles=8x, Birds=5x Number of birds in the zoo?St 1) says 11x=8x+12 Solving for x we get x=4 So, number of birds=5x=5*4= 20 sufficient.St 2) says if zoo acquired 16 more mammals, the ratio of mammals to birds would be 3:1 therefore (11x+16):5x=3:1 Solving for x we get x= 4 So, statement 2 is Sufficient to count the number of birds i.e, 5x or 5*4= 20 Answer is D.
_________________
"Success is not as glamorous as people tell you. It's a lot of hours spent in the darkness."



Intern
Joined: 19 Dec 2014
Posts: 35

Re: A certain zoo has mammal and reptiles and birds, and no other animals. [#permalink]
Show Tags
28 Sep 2015, 11:36
Given: M : R : B = 11 : 8 : 5
Say x is a multiplier,
No of mammals = 11x No of Reptiples = 8x No of birds = 5x
Statement 1:
11x = 8x +12 x = 4
No of birds = 20.
Sufficient
Statement 2:
ratio of M: B after adding 16 mammals
(11x + 16) / 5x = 3: 1
solving we get x = 4, Birds = 20.
Sufficient
Answer = D



Intern
Joined: 14 Mar 2015
Posts: 34

Re: A certain zoo has mammal and reptiles and birds, and no other animals. [#permalink]
Show Tags
28 Sep 2015, 11:50
Bunuel wrote: A certain zoo has mammal and reptiles and birds, and no other animals. The ratio of mammals to reptiles to birds is 11: 8:5. How many birds are in the zoo?
(1) there are twelve more mammals in the zoo than there are reptiles
(2) if the zoo acquired 16 more mammals, the ratio of mammals to birds would be 3:1
Kudos for a correct solution. Let, the number of animals be  mammals  11x reptiles  8x birds  5x We need to find the value of 5x. Analysis (1) mammals = reptiles + 12 or 11x = 8x +12; Clearly, this can be solved for x and therefore we can find out number of birds from 5x. So SUFFICIENT(2) if mammals population increase from 11x to 11x + 16, the ratio of mammals to birds will become 3:1 i.e. \(\frac{11x+16}{5x}\) = \(\frac{3}{1}\). This can also be solved for x, so again we can find the number of birds from 5x. So SUFFIENT. So correct answer is D.
_________________
It ain’t about how hard you hit. It’s about how hard you can get hit and keep moving forward; how much you can take and keep moving forward. That’s how winning is done!



Manager
Joined: 01 Jun 2013
Posts: 122

A certain zoo has mammal and reptiles and birds, and no other animals. [#permalink]
Show Tags
28 Sep 2015, 12:22
A certain zoo has mammal and reptiles and birds, and no other animals. The ratio of mammals to reptiles to birds is 11: 8:5. How many birds are in the zoo? (1) there are twelve more mammals in the zoo than there are reptiles (2) if the zoo acquired 16 more mammals, the ratio of mammals to birds would be 3:1 M: 11X R: 8X B: 5X Statement 1  11X8X=3X=12, then X=4  # of birds=5*4=20 >> Sufficient Statement 2  (11X+16)/5X=3, then X=4  # of birds=5*4=20>> Sufficient Answer is D.
_________________
Please kindly click on "+1 Kudos", if you think my post is useful



Manager
Joined: 23 Aug 2012
Posts: 73
Concentration: Technology

Re: A certain zoo has mammal and reptiles and birds, and no other animals. [#permalink]
Show Tags
30 Sep 2015, 06:19
I believe the answer is D. Please see below for explanation.
0) From the question we get that the ratio of Mammals to reptiles to birds is 11:8:5 and we are asked how many birds are there in the zoo?
(1) There are twelve more mammals in the zoo than there are reptiles
From this we get M = R +12. I number the number plugin approach as I didn't remember I could use the ratios to find x.
M:R:B 11:8:5 different between M and R = 3 22:16:10 different between M and R = 6 33:24:15 different between M and R = 9 44:32:20 different between M and R = 12
Thus the number of Birds is 20. Sufficient.
(2) if the zoo acquired 16 more mammals, the ratio of mammals to birds would be 3:1
For this we get (M + 16 / B ) = 3 : 1 and from the question stem we get that M / B = 11 / 5 thus 2 equations and 2 unknowns. Sufficient.
Answer D



Manager
Joined: 02 Jan 2017
Posts: 81
Location: Pakistan
Concentration: Finance, Technology
GPA: 3.41
WE: Business Development (Accounting)

Re: A certain zoo has mammal and reptiles and birds, and no other animals. [#permalink]
Show Tags
18 Dec 2017, 02:32
Jonas84 wrote: I believe the answer is D. Please see below for explanation.
0) From the question we get that the ratio of Mammals to reptiles to birds is 11:8:5 and we are asked how many birds are there in the zoo?
(1) There are twelve more mammals in the zoo than there are reptiles
From this we get M = R +12. I number the number plugin approach as I didn't remember I could use the ratios to find x.
M:R:B 11:8:5 different between M and R = 3 22:16:10 different between M and R = 6 33:24:15 different between M and R = 9 44:32:20 different between M and R = 12
Thus the number of Birds is 20. Sufficient.
(2) if the zoo acquired 16 more mammals, the ratio of mammals to birds would be 3:1
For this we get (M + 16 / B ) = 3 : 1 and from the question stem we get that M / B = 11 / 5 thus 2 equations and 2 unknowns. Sufficient.
Answer D Can someone elaborate on the highlighted approach?




Re: A certain zoo has mammal and reptiles and birds, and no other animals.
[#permalink]
18 Dec 2017, 02:32






