In a zoo, the ratio of the number of cheetahs to the number

Question

In a zoo, the ratio of the number of cheetahs to the number of pandas is 1 : 3 and was the same five years ago. If the increase in the number of cheetahs in the zoo since then is 5, then what is the increase in the number of pandas?

(A) 2
(B) 3
(C) 5
(D) 10
(E) 15

Source: Nova GMAT
Difficulty Level: 500

Show Answer

Official Answer

E

(A) 2
(B) 3
(C) 5
(D) 10
(E) 15

Source:   Nova GMAT  
Difficulty Level:   500

DayOfTheJackal · Answer

One short cut to solve the problem is

c:p = 1:3
c increased to 6
=> 1:3 = 6:x 
=> x = 18
=>p increased by 15
E is the answer

cyberjadugar · Answer

Hi,

Ratio of cheetah to panda = 1:3
or  \frac {x}{3x} 
so, if number of cheetah increases by 5 such that the ratio must remain same, then
 \frac {x+5x}{3(x+5x)} = \frac {x+5x}{3x+15x} 
so increase in the number of panda would be in multiple of 15.

Thus, Answer (E)

Regards,

rajathpanta · Answer

Consider the number of cheetahs = 10;...> no of pandas=30
Therefore if number of cheetas is 5 more=10+5=15 then pandas must be 3 times more=15*3=45.
Increase in the number of pandas=45-30=15
 
  Ans-D

EMPOWERgmatRichC · Answer

Hi All,

When a ratio question involves "relatively small" numbers, you can quickly "brute force" the prompt and get to the correct answer.

Here, we know the ratio of cheetahs to pandas is 1:3. Since you can't have a "fraction" of an animal, that means that the number of cheetahs is a multiple of 1 and the number of pandas is the equivalent multiple of 3.

Here is a quick list of the immediate possibilities....

C:P
1:3
1 and 3
2 and 6
3 and 9
4 and 12
5 and 15
6 and 18
Etc.

We're told that the ratio of cheetahs to pandas stayed the same and that over the last 5 years there was an increase of 5 cheetahs.

If we "start" with 1 cheetah and 3 pandas, then increase the number of cheetahs by 5.....we'll have 6 cheetahs and 18 pandas....Thus, the number of pandas increased from 3 to 18 (an increase of 15.

Final Answer:  E

GMAT assassins aren't born, they're made,
Rich

KarishmaB · Answer

Use simple logic:

Given the ratio 1:3, if you increase 1 by 5, you will need to increase 3 by 3*5 to retain the ratio

\frac{1}{3} = \frac{1 + x}{3 + 3x} = \frac{1(1+x)}{3(1+x)} = \frac{1}{3}

So, if you increase numerator by 5, denominator must be increased by 3*5 = 15

GauravSolanky · Answer

One simple logic would be;If two things are in ratio then over the period of time if there is any increment/decrement and even after that they maintain same ratio then increment/decrement will also be in the same ratio.

Now and 5 years back ratio is= 1:3
Increment in C= 5
Hence, Increment in P will be 15

Hope this helps !

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In a zoo, the ratio of the number of cheetahs to the number

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