Zoo Animals - Easy but a tricky one

[mevicks]

In a certain zoo, the number of giraffes is 40% the number of chimps, and the number of lions is 55% the number of zebras. If it is given that the number of zebras is approximately 90% the number of chimps, which of the following can be true?

A) For every chimp, there are approximately 2 lions present
B) For every 5 lions, there are approximately 6 giraffes present
C) For every 4 lions, there is exactly one giraffe present
D) For every 5 lions, there are approximately 4 giraffes present
E) For every 4 giraffes, there is a lion present

OA D

Regards,
Vivek

[Uva@90]

In a certain zoo, the number of giraffes is 40% the number of chimps, and the number of lions is 55% the number of zebras. If it is given that the number of zebras is approximately 90% the number of chimps, which of the following can be true?

A) For every chimp, there are approximately 2 lions present
B) For every 5 lions, there are approximately 6 giraffes present
C) For every 4 lions, there is exactly one giraffe present
D) For every 5 lions, there are approximately 4 giraffes present
E) For every 4 giraffes, there is a lion present

OA after a few responses

Regards,
Vivek

Hi Vivek is OA D ?

[sanjoy18]

Let chimps=200
Giraffes= 80
Zebras= 180
Lions= 99

Now Lion is to Girafffe = 99:80
= 5:4 (approximately)
Hence D

[mevicks]

Smart Numbers Approach:
Let C = 100
G = 40
Z = 90
L = 0.55 * 90 = 50 approx
For every 5 lions there are 4 giraffes.

Algebraic Approach:
G = 0.4 C
L = 0.55 Z
Z = 0.9 C (approx)

Do a quick vertical scan of the answers, we need the relationships C--L & L--G. Substitute the above equations to form the relationships
L = 0.55 * 0.9 C = 0.5 C = C/2 (approx)
also from the above relationship C = 2 L
G = 0.4 * 2 L = 0.8 L
Substitute the answer choices to check the relationship, only L = 5 & G = 4 works.

[spoiler]Answer : D[/spoiler]

Regards,
Vivek

[GMATGuruNY]

In a certain zoo, the number of giraffes is 40% the number of chimps, and the number of lions is 55% the number of zebras. If it is given that the number of zebras is approximately 90% the number of chimps, which of the following can be true?

A) For every chimp, there are approximately 2 lions present
B) For every 5 lions, there are approximately 6 giraffes present
C) For every 4 lions, there is exactly one giraffe present
D) For every 5 lions, there are approximately 4 giraffes present
E) For every 4 giraffes, there is a lion present

OA after a few responses

Regards,
Vivek

The number of giraffes is 40% the number of chimps.
G:C = 40:100.
The number of lions is 55% the number of zebras.
L:Z = 55:100.

If Z=C, we get:
G:L:Z:C = 40:55100.
Since Z is actually approximately 90% of C, the values for L:Z must decrease by about 10%:
G:L:Z:C = 40:50:90:100.

G:L = 40:50 = 4:5, supporting answer choice D:
For every 5 lions, there are approximately 4 giraffes present.

The correct answer is D.

[mevicks]

Hi Mitch,

Why is the 10% reduction not made for G:L ?


Regards,
Vivek

[GMATGuruNY]

Hi Mitch,

Why is the 10% reduction not made for G:L ?


Regards,
Vivek

Only one constraint is given for G:
G:C = 40:100.
When the ratio is altered from G:L:Z:C = 40:55100 to G:L:Z:C = 40:50:90:100, G:C = 40:100 in each case, so there is no reason to change the value of G.