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

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Manager
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In a zoo, the ratio of the number of cheetahs to the number  [#permalink]

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Updated on: 08 Jul 2012, 02:45
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5% (low)

Question Stats:

90% (01:06) correct 10% (01:17) wrong based on 124 sessions

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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

Originally posted by farukqmul on 07 Jul 2012, 22:52.
Last edited by Bunuel on 08 Jul 2012, 02:45, edited 1 time in total.
Edited the question.
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08 Jul 2012, 00:15
1
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
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08 Jul 2012, 02:24
farukqmul wrote:
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

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.

Regards,
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Re: In a zoo, the ratio of the number of cheetahs to the number  [#permalink]

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27 Jul 2012, 04:02
1
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
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Re: In a zoo, the ratio of the number of cheetahs to the number  [#permalink]

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04 Mar 2015, 17:43
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.

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Re: In a zoo, the ratio of the number of cheetahs to the number  [#permalink]

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04 Mar 2015, 22:12
farukqmul wrote:
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

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
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Re: In a zoo, the ratio of the number of cheetahs to the number  [#permalink]

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05 Mar 2015, 08:03
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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Re: In a zoo, the ratio of the number of cheetahs to the number  [#permalink]

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10 Feb 2018, 07:25
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Re: In a zoo, the ratio of the number of cheetahs to the number &nbs [#permalink] 10 Feb 2018, 07:25
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